Dataframe commands (#3502)

* Sample command

* Join command with checks

* More dataframes commands

* Groupby and aggregate commands

* Missing feature dataframe flag

* Renamed file

* New commands for dataframes

* error parser and df reference

* filter command for dataframes

* removed name from nu_dataframe

* commands to save to parquet and csv

crates/nu-command/Cargo.toml

@@ -102,7 +102,7 @@ zip = { version = "0.5.9", optional = true }
 [dependencies.polars]
 version = "0.13.4"
 optional = true
-features = ["parquet", "json", "random"]
+features = ["parquet", "json", "random", "pivot"]
 
 [target.'cfg(unix)'.dependencies]
 umask = "1.0.0"

crates/nu-command/src/commands.rs

@@ -192,8 +192,9 @@ pub(crate) use any::Command as Any;
 #[cfg(feature = "dataframe")]
 pub(crate) use dataframe::{
     DataFrame, DataFrameAggregate, DataFrameConvert, DataFrameDTypes, DataFrameDrop,
-    DataFrameGroupBy, DataFrameJoin, DataFrameList, DataFrameLoad, DataFrameSample,
-    DataFrameSelect, DataFrameShow,
+    DataFrameDummies, DataFrameGroupBy, DataFrameHead, DataFrameJoin, DataFrameList, DataFrameLoad,
+    DataFrameMelt, DataFramePivot, DataFrameSample, DataFrameSelect, DataFrameShow, DataFrameSlice,
+    DataFrameTail, DataFrameToCsv, DataFrameToParquet, DataFrameWhere,
 };
 pub(crate) use enter::Enter;
 pub(crate) use every::Every;

crates/nu-command/src/commands/dataframe/aggregate.rs

@@ -1,4 +1,4 @@
-use crate::prelude::*;
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
 use nu_protocol::{
@@ -6,7 +6,7 @@ use nu_protocol::{
     Signature, SyntaxShape, UntaggedValue, Value,
 };
 use nu_source::Tagged;
-use polars::frame::groupby::GroupBy;
+use polars::{frame::groupby::GroupBy, prelude::PolarsError};
 
 use super::utils::convert_columns;
 
@@ -101,20 +101,19 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        aggregate(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "Aggregate sum by grouping by column a and summing on col b",
-            example:
-                "echo [[a b]; [one 1] [one 2]] | pls convert | pls groupby [a] | pls aggregate sum",
+            example: "[[a b]; [one 1] [one 2]] | pls convert | pls groupby [a] | pls aggregate sum",
             result: None,
         }]
     }
 }
 
-fn aggregate(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -132,12 +131,12 @@ fn aggregate(args: CommandArgs) -> Result<OutputStream, ShellError> {
         None => (None, Span::unknown()),
     };
 
-    // The operation is only done in one dataframe. Only one input is
+    // The operation is only done in one groupby. Only one input is
     // expected from the InputStream
     match args.input.next() {
         None => Err(ShellError::labeled_error(
             "No input received",
-            "missing dataframe input from stream",
+            "missing groupby input from stream",
             &tag,
         )),
         Some(value) => {
@@ -191,12 +190,11 @@ fn perform_aggregation(
         Operation::Count => groupby.count(),
     }
     .map_err(|e| {
-        let span = if e.to_string().contains("Not found") {
-            agg_span
-        } else {
-            &operation_tag.span
+        let span = match &e {
+            PolarsError::NotFound(_) => agg_span,
+            _ => &operation_tag.span,
         };
 
-        ShellError::labeled_error("Aggregation error", format!("{}", e), span)
+        parse_polars_error::<&str>(&e, span, None)
     })
 }

crates/nu-command/src/commands/dataframe/convert.rs

@@ -36,7 +36,7 @@ impl WholeStreamCommand for DataFrame {
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "Takes an input stream and converts it to a polars dataframe",
-            example: "echo [[a b];[1 2] [3 4]] | pls convert",
+            example: "[[a b];[1 2] [3 4]] | pls convert",
             result: None,
         }]
     }

crates/nu-command/src/commands/dataframe/drop.rs

@@ -6,7 +6,7 @@ use nu_protocol::{
     Signature, SyntaxShape, UntaggedValue, Value,
 };
 
-use super::utils::convert_columns;
+use super::utils::{convert_columns, parse_polars_error};
 
 pub struct DataFrame;
 
@@ -28,19 +28,19 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        drop(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "drop column a",
-            example: "echo [[a b]; [1 2] [3 4]] | pls convert | pls drop [a]",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls drop [a]",
             result: None,
         }]
     }
 }
 
-fn drop(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -55,15 +55,13 @@ fn drop(args: CommandArgs) -> Result<OutputStream, ShellError> {
             &tag,
         )),
         Some(value) => {
-            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                dataframe: Some(ref df),
-                ..
-            })) = value.value
-            {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                // Dataframe with the first selected column
                 let new_df = match col_string.iter().next() {
-                    Some(col) => df.drop(col).map_err(|e| {
-                        ShellError::labeled_error("Join error", format!("{}", e), &col_span)
-                    }),
+                    Some(col) => df
+                        .as_ref()
+                        .drop(col)
+                        .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None)),
                     None => Err(ShellError::labeled_error(
                         "Empty names list",
                         "No column names where found",
@@ -71,10 +69,12 @@ fn drop(args: CommandArgs) -> Result<OutputStream, ShellError> {
                     )),
                 }?;
 
+                // If there are more columns in the drop selection list, these
+                // are added from the resulting dataframe
                 let res = col_string.iter().skip(1).try_fold(new_df, |new_df, col| {
-                    new_df.drop(col).map_err(|e| {
-                        ShellError::labeled_error("Drop error", format!("{}", e), &col_span)
-                    })
+                    new_df
+                        .drop(col)
+                        .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))
                 })?;
 
                 let value = Value {

crates/nu-command/src/commands/dataframe/dtypes.rs

@@ -1,10 +1,7 @@
 use crate::prelude::*;
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
-use nu_protocol::{
-    dataframe::{NuDataFrame, PolarsData},
-    Signature, TaggedDictBuilder, UntaggedValue,
-};
+use nu_protocol::{dataframe::PolarsData, Signature, TaggedDictBuilder, UntaggedValue};
 
 pub struct DataFrame;
 
@@ -22,19 +19,19 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        dtypes(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "drop column a",
-            example: "echo [[a b]; [1 2] [3 4]] | pls convert | pls dtypes",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls dtypes",
             result: None,
         }]
     }
 }
 
-fn dtypes(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -45,28 +42,26 @@ fn dtypes(args: CommandArgs) -> Result<OutputStream, ShellError> {
             &tag,
         )),
         Some(value) => {
-            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                dataframe: Some(df),
-                ..
-            })) = value.value
-            {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
                 let col_names = df
+                    .as_ref()
                     .get_column_names()
                     .iter()
                     .map(|v| v.to_string())
                     .collect::<Vec<String>>();
 
-                let values =
-                    df.dtypes()
-                        .into_iter()
-                        .zip(col_names.into_iter())
-                        .map(move |(dtype, name)| {
-                            let mut data = TaggedDictBuilder::new(tag.clone());
-                            data.insert_value("column", name.as_ref());
-                            data.insert_value("dtype", format!("{}", dtype));
+                let values = df
+                    .as_ref()
+                    .dtypes()
+                    .into_iter()
+                    .zip(col_names.into_iter())
+                    .map(move |(dtype, name)| {
+                        let mut data = TaggedDictBuilder::new(tag.clone());
+                        data.insert_value("column", name.as_ref());
+                        data.insert_value("dtype", format!("{}", dtype));
 
-                            data.into_value()
-                        });
+                        data.into_value()
+                    });
 
                 Ok(OutputStream::from_stream(values))
             } else {

crates/nu-command/src/commands/dataframe/dummies.rs

@@ -0,0 +1,76 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, UntaggedValue, Value,
+};
+
+use super::utils::parse_polars_error;
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls to_dummies"
+    }
+
+    fn usage(&self) -> &str {
+        "Creates a new dataframe with dummy variables"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls select")
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Create new dataframe with dummy variables",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls to_dummies",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                let res = df.as_ref().to_dummies().map_err(|e| {
+                    parse_polars_error(
+                        &e,
+                        &tag.span,
+                        Some("The only allowed column types for dummies are String or Int"),
+                    )
+                })?;
+
+                let value = Value {
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                    tag: tag.clone(),
+                };
+
+                Ok(OutputStream::one(value))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No dataframe in stream",
+                    "no dataframe found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}

crates/nu-command/src/commands/dataframe/groupby.rs

@@ -1,4 +1,4 @@
-use crate::prelude::*;
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
 use nu_protocol::{
@@ -28,19 +28,19 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        groupby(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "Grouping by column a",
-            example: "echo [[a b]; [one 1] [one 2]] | pls convert | pls groupby [a]",
+            example: "[[a b]; [one 1] [one 2]] | pls convert | pls groupby [a]",
             result: None,
         }]
     }
 }
 
-fn groupby(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -58,24 +58,20 @@ fn groupby(args: CommandArgs) -> Result<OutputStream, ShellError> {
         )),
         Some(value) => {
             if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(nu_df)) = value.value {
-                let df = match nu_df.dataframe {
-                    Some(df) => df,
-                    None => unreachable!("No dataframe in nu_dataframe"),
-                };
-
                 // This is the expensive part of the groupby; to create the
                 // groups that will be used for grouping the data in the
                 // dataframe. Once it has been done these values can be stored
-                // in the NuGroupBy
-                let groupby = df.groupby(&columns_string).map_err(|e| {
-                    ShellError::labeled_error("Groupby error", format!("{}", e), col_span)
-                })?;
+                // in a NuGroupBy
+                let groupby = nu_df
+                    .as_ref()
+                    .groupby(&columns_string)
+                    .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))?;
 
                 let groups = groupby.get_groups().to_vec();
                 let groupby = Value {
                     tag: value.tag,
                     value: UntaggedValue::DataFrame(PolarsData::GroupBy(NuGroupBy::new(
-                        NuDataFrame::new_with_name(df, nu_df.name),
+                        NuDataFrame::new(nu_df.as_ref().clone()),
                         columns_string,
                         groups,
                     ))),

crates/nu-command/src/commands/dataframe/head.rs

@@ -0,0 +1,80 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+use nu_source::Tagged;
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls head"
+    }
+
+    fn usage(&self) -> &str {
+        "Creates new dataframe with head rows"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls select").optional(
+            "n_rows",
+            SyntaxShape::Number,
+            "Number of rows for head",
+        )
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Create new dataframe with head rows",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls head",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+    let rows: Option<Tagged<usize>> = args.opt(0)?;
+
+    let rows = match rows {
+        Some(val) => val.item,
+        None => 5,
+    };
+
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                let res = df.as_ref().head(Some(rows));
+
+                let value = Value {
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                    tag: tag.clone(),
+                };
+
+                Ok(OutputStream::one(value))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No dataframe in stream",
+                    "no dataframe found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}

crates/nu-command/src/commands/dataframe/join.rs

@@ -6,7 +6,7 @@ use nu_protocol::{
     Signature, SyntaxShape, UntaggedValue, Value,
 };
 
-use super::utils::convert_columns;
+use super::utils::{convert_columns, parse_polars_error};
 
 use polars::prelude::JoinType;
 
@@ -45,7 +45,7 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        join(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -58,14 +58,14 @@ impl WholeStreamCommand for DataFrame {
             Example {
                 description: "right join dataframe",
                 example:
-                    "echo [[a b]; [1 2] [3 4] [5 6]] | pls convert | pls join $right [b] [b] -t right",
+                    "[[a b]; [1 2] [3 4] [5 6]] | pls convert | pls join $right [b] [b] -t right",
                 result: None,
             },
         ]
     }
 }
 
-fn join(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -102,33 +102,21 @@ fn join(args: CommandArgs) -> Result<OutputStream, ShellError> {
             &tag,
         )),
         Some(value) => {
-            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                dataframe: Some(ref df),
-                ..
-            })) = value.value
-            {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
                 let res = match r_df.value {
-                    UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                        dataframe: Some(r_df),
-                        ..
-                    })) => {
+                    UntaggedValue::DataFrame(PolarsData::EagerDataFrame(r_df)) => {
                         // Checking the column types before performing the join
                         check_column_datatypes(
-                            df,
+                            df.as_ref(),
                             &l_col_string,
                             &l_col_span,
                             &r_col_string,
                             &r_col_span,
                         )?;
 
-                        df.join(&r_df, &l_col_string, &r_col_string, join_type)
-                            .map_err(|e| {
-                                ShellError::labeled_error(
-                                    "Join error",
-                                    format!("{}", e),
-                                    &l_col_span,
-                                )
-                            })
+                        df.as_ref()
+                            .join(r_df.as_ref(), &l_col_string, &r_col_string, join_type)
+                            .map_err(|e| parse_polars_error::<&str>(&e, &l_col_span, None))
                     }
                     _ => Err(ShellError::labeled_error(
                         "Not a dataframe",
@@ -180,11 +168,11 @@ fn check_column_datatypes<T: AsRef<str>>(
     for (l, r) in l_cols.iter().zip(r_cols.iter()) {
         let l_series = df
             .column(l.as_ref())
-            .map_err(|e| ShellError::labeled_error("Join error", format!("{}", e), l_col_span))?;
+            .map_err(|e| parse_polars_error::<&str>(&e, &l_col_span, None))?;
 
         let r_series = df
             .column(r.as_ref())
-            .map_err(|e| ShellError::labeled_error("Join error", format!("{}", e), r_col_span))?;
+            .map_err(|e| parse_polars_error::<&str>(&e, &r_col_span, None))?;
 
         if l_series.dtype() != r_series.dtype() {
             return Err(ShellError::labeled_error_with_secondary(

crates/nu-command/src/commands/dataframe/list.rs

@@ -1,10 +1,7 @@
 use crate::prelude::*;
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
-use nu_protocol::{
-    dataframe::{NuDataFrame, PolarsData},
-    Signature, TaggedDictBuilder, UntaggedValue,
-};
+use nu_protocol::{dataframe::PolarsData, Signature, TaggedDictBuilder, UntaggedValue};
 
 pub struct DataFrame;
 
@@ -30,21 +27,26 @@ impl WholeStreamCommand for DataFrame {
             .get_vars()
             .into_iter()
             .filter_map(|(name, value)| {
-                if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                    dataframe: Some(df),
-                    name: file_name,
-                })) = &value.value
-                {
+                if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = &value.value {
                     let mut data = TaggedDictBuilder::new(value.tag.clone());
 
-                    let rows = df.height();
-                    let cols = df.width();
+                    let rows = df.as_ref().height();
+                    let cols = df.as_ref().width();
 
                     data.insert_value("name", name.as_ref());
-                    data.insert_value("file", file_name.as_ref());
                     data.insert_value("rows", format!("{}", rows));
                     data.insert_value("columns", format!("{}", cols));
 
+                    match value.tag.anchor {
+                        Some(AnchorLocation::File(name)) => data.insert_value("location", name),
+                        Some(AnchorLocation::Url(name)) => data.insert_value("location", name),
+                        Some(AnchorLocation::Source(text)) => {
+                            let loc_name = text.slice(0..text.end);
+                            data.insert_value("location", loc_name.text)
+                        }
+                        None => data.insert_value("location", "stream"),
+                    }
+
                     Some(data.into_value())
                 } else {
                     None

crates/nu-command/src/commands/dataframe/load.rs

@@ -1,6 +1,6 @@
 use std::path::PathBuf;
 
-use crate::prelude::*;
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
 use nu_engine::{EvaluatedCommandArgs, WholeStreamCommand};
 use nu_errors::ShellError;
 use nu_protocol::{
@@ -28,7 +28,7 @@ impl WholeStreamCommand for DataFrame {
             .required(
                 "file",
                 SyntaxShape::FilePath,
-                "the file path to load values from",
+                "file path to load values from",
             )
             .named(
                 "delimiter",
@@ -62,7 +62,7 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        create_from_file(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
@@ -74,7 +74,7 @@ impl WholeStreamCommand for DataFrame {
     }
 }
 
-fn create_from_file(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let args = args.evaluate_once()?;
     let file: Tagged<PathBuf> = args.req(0)?;
@@ -101,21 +101,24 @@ fn create_from_file(args: CommandArgs) -> Result<OutputStream, ShellError> {
         Ok(name) => name,
         Err(e) => {
             return Err(ShellError::labeled_error(
-                "Error with file name",
+                "File Name Error",
                 format!("{:?}", e),
                 &file.tag,
             ))
         }
     };
 
-    let init = InputStream::one(
-        UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new_with_name(
-            df, file_name,
-        )))
-        .into_value(&tag),
-    );
+    let df_tag = Tag {
+        anchor: Some(AnchorLocation::File(file_name.to_string())),
+        span: tag.span,
+    };
 
-    Ok(init.to_output_stream())
+    let tagged_value = Value {
+        value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(df))),
+        tag: df_tag,
+    };
+
+    Ok(InputStream::one(tagged_value).to_output_stream())
 }
 
 fn from_parquet(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, ShellError> {
@@ -128,7 +131,7 @@ fn from_parquet(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame
 
     reader
         .finish()
-        .map_err(|e| ShellError::labeled_error("Error with file", format!("{:?}", e), &file.tag))
+        .map_err(|e| parse_polars_error::<&str>(&e, &file.tag.span, None))
 }
 
 fn from_json(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, ShellError> {
@@ -141,7 +144,7 @@ fn from_json(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, S
 
     reader
         .finish()
-        .map_err(|e| ShellError::labeled_error("Error with file", format!("{:?}", e), &file.tag))
+        .map_err(|e| parse_polars_error::<&str>(&e, &file.tag.span, None))
 }
 
 fn from_csv(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, ShellError> {
@@ -152,9 +155,8 @@ fn from_csv(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, Sh
     let skip_rows: Option<Tagged<usize>> = args.get_flag("skip_rows")?;
     let columns: Option<Vec<Value>> = args.get_flag("columns")?;
 
-    let csv_reader = CsvReader::from_path(&file.item).map_err(|e| {
-        ShellError::labeled_error("Unable to parse file", format!("{}", e), &file.tag)
-    })?;
+    let csv_reader = CsvReader::from_path(&file.item)
+        .map_err(|e| parse_polars_error::<&str>(&e, &file.tag.span, None))?;
 
     let csv_reader = match delimiter {
         None => csv_reader,
@@ -212,10 +214,6 @@ fn from_csv(args: EvaluatedCommandArgs) -> Result<polars::prelude::DataFrame, Sh
 
     match csv_reader.finish() {
         Ok(csv_reader) => Ok(csv_reader),
-        Err(e) => Err(ShellError::labeled_error(
-            "Error while parsing dataframe",
-            format!("{}", e),
-            &file.tag,
-        )),
+        Err(e) => Err(parse_polars_error::<&str>(&e, &file.tag.span, None)),
     }
 }

crates/nu-command/src/commands/dataframe/melt.rs

@@ -0,0 +1,131 @@
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+use super::utils::convert_columns;
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls melt"
+    }
+
+    fn usage(&self) -> &str {
+        "Unpivot a DataFrame from wide to long format"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls join")
+            .required("id_columns", SyntaxShape::Table, "Id columns for melting")
+            .required(
+                "value_columns",
+                SyntaxShape::Table,
+                "columns used as value columns",
+            )
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "melt dataframe",
+            example: "[[a b]; [a 2] [b 4] [a 6]] | pls convert | pls melt [a] [b]",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+
+    let id_col: Vec<Value> = args.req(0)?;
+    let val_col: Vec<Value> = args.req(1)?;
+
+    let (id_col_string, id_col_span) = convert_columns(&id_col, &tag)?;
+    let (val_col_string, val_col_span) = convert_columns(&val_col, &tag)?;
+
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                check_column_datatypes(df.as_ref(), &id_col_string, &id_col_span)?;
+                check_column_datatypes(df.as_ref(), &val_col_string, &val_col_span)?;
+
+                let res = df
+                    .as_ref()
+                    .melt(&id_col_string, &val_col_string)
+                    .map_err(|e| parse_polars_error::<&str>(&e, &tag.span, None))?;
+
+                let value = Value {
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                    tag: tag.clone(),
+                };
+
+                Ok(OutputStream::one(value))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No dataframe in stream",
+                    "no dataframe found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}
+
+fn check_column_datatypes<T: AsRef<str>>(
+    df: &polars::prelude::DataFrame,
+    cols: &[T],
+    col_span: &Span,
+) -> Result<(), ShellError> {
+    if cols.len() == 0 {
+        return Err(ShellError::labeled_error(
+            "Merge error",
+            "empty column list",
+            col_span,
+        ));
+    }
+
+    // Checking if they are same type
+    if cols.len() > 1 {
+        for w in cols.windows(2) {
+            let l_series = df
+                .column(w[0].as_ref())
+                .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))?;
+
+            let r_series = df
+                .column(w[1].as_ref())
+                .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))?;
+
+            if l_series.dtype() != r_series.dtype() {
+                return Err(ShellError::labeled_error_with_secondary(
+                    "Merge error",
+                    "found different column types in list",
+                    col_span,
+                    format!(
+                        "datatypes {} and {} are incompatible",
+                        l_series.dtype(),
+                        r_series.dtype()
+                    ),
+                    col_span,
+                ));
+            }
+        }
+    }
+
+    Ok(())
+}

crates/nu-command/src/commands/dataframe/mod.rs

@@ -3,24 +3,42 @@ pub mod command;
 pub mod convert;
 pub mod drop;
 pub mod dtypes;
+pub mod dummies;
 pub mod groupby;
+pub mod head;
 pub mod join;
 pub mod list;
 pub mod load;
+pub mod melt;
+pub mod pivot;
 pub mod sample;
 pub mod select;
 pub mod show;
+pub mod slice;
+pub mod tail;
+pub mod to_csv;
+pub mod to_parquet;
 pub(crate) mod utils;
+pub mod where_;
 
 pub use aggregate::DataFrame as DataFrameAggregate;
 pub use command::Command as DataFrame;
 pub use convert::DataFrame as DataFrameConvert;
 pub use drop::DataFrame as DataFrameDrop;
 pub use dtypes::DataFrame as DataFrameDTypes;
+pub use dummies::DataFrame as DataFrameDummies;
 pub use groupby::DataFrame as DataFrameGroupBy;
+pub use head::DataFrame as DataFrameHead;
 pub use join::DataFrame as DataFrameJoin;
 pub use list::DataFrame as DataFrameList;
 pub use load::DataFrame as DataFrameLoad;
+pub use melt::DataFrame as DataFrameMelt;
+pub use pivot::DataFrame as DataFramePivot;
 pub use sample::DataFrame as DataFrameSample;
 pub use select::DataFrame as DataFrameSelect;
 pub use show::DataFrame as DataFrameShow;
+pub use slice::DataFrame as DataFrameSlice;
+pub use tail::DataFrame as DataFrameTail;
+pub use to_csv::DataFrame as DataFrameToCsv;
+pub use to_parquet::DataFrame as DataFrameToParquet;
+pub use where_::DataFrame as DataFrameWhere;

crates/nu-command/src/commands/dataframe/pivot.rs

@@ -0,0 +1,193 @@
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, SyntaxShape, UntaggedValue, Value,
+};
+use nu_source::Tagged;
+
+use polars::prelude::DataType;
+
+enum Operation {
+    First,
+    Sum,
+    Min,
+    Max,
+    Mean,
+    Median,
+}
+
+impl Operation {
+    fn from_tagged(name: &Tagged<String>) -> Result<Operation, ShellError> {
+        match name.item.as_ref() {
+            "first" => Ok(Operation::First),
+            "sum" => Ok(Operation::Sum),
+            "min" => Ok(Operation::Min),
+            "max" => Ok(Operation::Max),
+            "mean" => Ok(Operation::Mean),
+            "median" => Ok(Operation::Median),
+            _ => Err(ShellError::labeled_error_with_secondary(
+                "Operation not fount",
+                "Operation does not exist for pivot",
+                &name.tag,
+                "Perhaps you want: first, sum, min, max, mean, median",
+                &name.tag,
+            )),
+        }
+    }
+}
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls pivot"
+    }
+
+    fn usage(&self) -> &str {
+        "Performs a pivot operation on a groupby object"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls pivot")
+            .required(
+                "pivot column",
+                SyntaxShape::String,
+                "pivot column to perform pivot",
+            )
+            .required(
+                "value column",
+                SyntaxShape::String,
+                "value column to perform pivot",
+            )
+            .required("operation", SyntaxShape::String, "aggregate operation")
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Pivot a dataframe on b and aggregation on col c",
+            example:
+                "[[a b c]; [one x 1] [two y 2]] | pls convert | pls groupby [a] | pls pivot b c sum",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+
+    // Extracting the pivot col from arguments
+    let pivot_col: Tagged<String> = args.req(0)?;
+
+    // Extracting the value col from arguments
+    let value_col: Tagged<String> = args.req(1)?;
+
+    let operation: Tagged<String> = args.req(2)?;
+    let op = Operation::from_tagged(&operation)?;
+
+    // The operation is only done in one groupby. Only one input is
+    // expected from the InputStream
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing groupby input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::GroupBy(nu_groupby)) = value.value {
+                let df_ref = nu_groupby.as_ref();
+
+                check_pivot_column(df_ref, &pivot_col)?;
+                check_value_column(df_ref, &value_col)?;
+
+                let mut groupby = nu_groupby.to_groupby()?;
+
+                let pivot = groupby.pivot(pivot_col.item.as_ref(), value_col.item.as_ref());
+
+                let res = match op {
+                    Operation::Mean => pivot.mean(),
+                    Operation::Sum => pivot.sum(),
+                    Operation::Min => pivot.min(),
+                    Operation::Max => pivot.max(),
+                    Operation::First => pivot.first(),
+                    Operation::Median => pivot.median(),
+                }
+                .map_err(|e| parse_polars_error::<&str>(&e, &tag.span, None))?;
+
+                let final_df = Value {
+                    tag,
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                };
+
+                Ok(OutputStream::one(final_df))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No groupby in stream",
+                    "no groupby found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}
+
+fn check_pivot_column(
+    df: &polars::prelude::DataFrame,
+    col: &Tagged<String>,
+) -> Result<(), ShellError> {
+    let series = df
+        .column(col.item.as_ref())
+        .map_err(|e| parse_polars_error::<&str>(&e, &col.tag.span, None))?;
+
+    match series.dtype() {
+        DataType::UInt8
+        | DataType::UInt16
+        | DataType::UInt32
+        | DataType::UInt64
+        | DataType::Int8
+        | DataType::Int16
+        | DataType::Int32
+        | DataType::Int64
+        | DataType::Utf8 => Ok(()),
+        _ => Err(ShellError::labeled_error(
+            "Pivot error",
+            format!("Unsupported datatype {}", series.dtype()),
+            col.tag.span,
+        )),
+    }
+}
+
+fn check_value_column(
+    df: &polars::prelude::DataFrame,
+    col: &Tagged<String>,
+) -> Result<(), ShellError> {
+    let series = df
+        .column(col.item.as_ref())
+        .map_err(|e| parse_polars_error::<&str>(&e, &col.tag.span, None))?;
+
+    match series.dtype() {
+        DataType::UInt8
+        | DataType::UInt16
+        | DataType::UInt32
+        | DataType::UInt64
+        | DataType::Int8
+        | DataType::Int16
+        | DataType::Int32
+        | DataType::Int64
+        | DataType::Float32
+        | DataType::Float64 => Ok(()),
+        _ => Err(ShellError::labeled_error(
+            "Pivot error",
+            format!("Unsupported datatype {}", series.dtype()),
+            col.tag.span,
+        )),
+    }
+}

crates/nu-command/src/commands/dataframe/sample.rs

@@ -1,4 +1,4 @@
-use crate::prelude::*;
+use crate::{commands::dataframe::utils::parse_polars_error, prelude::*};
 use nu_engine::WholeStreamCommand;
 use nu_errors::ShellError;
 use nu_protocol::{
@@ -37,26 +37,26 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        sample(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![
             Example {
                 description: "Sample rows from dataframe",
-                example: "echo [[a b]; [1 2] [3 4]] | pls load | pls sample -r 1",
+                example: "[[a b]; [1 2] [3 4]] | pls load | pls sample -r 1",
                 result: None,
             },
             Example {
                 description: "Shows sample row using fraction and replace",
-                example: "echo [[a b]; [1 2] [3 4] [5 6]] | pls load | pls sample -f 0.5 -e",
+                example: "[[a b]; [1 2] [3 4] [5 6]] | pls load | pls sample -f 0.5 -e",
                 result: None,
             },
         ]
     }
 }
 
-fn sample(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -71,18 +71,16 @@ fn sample(args: CommandArgs) -> Result<OutputStream, ShellError> {
             &tag,
         )),
         Some(value) => {
-            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                dataframe: Some(ref df),
-                ..
-            })) = value.value
-            {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
                 let res = match (rows, fraction) {
-                    (Some(rows), None) => df.sample_n(rows.item, replace).map_err(|e| {
-                        ShellError::labeled_error("Polars error", format!("{}", e), &rows.tag)
-                    }),
-                    (None, Some(frac)) => df.sample_frac(frac.item, replace).map_err(|e| {
-                        ShellError::labeled_error("Polars error", format!("{}", e), &frac.tag)
-                    }),
+                    (Some(rows), None) => df
+                        .as_ref()
+                        .sample_n(rows.item, replace)
+                        .map_err(|e| parse_polars_error::<&str>(&e, &rows.tag.span, None)),
+                    (None, Some(frac)) => df
+                        .as_ref()
+                        .sample_frac(frac.item, replace)
+                        .map_err(|e| parse_polars_error::<&str>(&e, &frac.tag.span, None)),
                     (Some(_), Some(_)) => Err(ShellError::labeled_error(
                         "Incompatible flags",
                         "Only one selection criterion allowed",

crates/nu-command/src/commands/dataframe/select.rs

@@ -6,7 +6,7 @@ use nu_protocol::{
     Signature, SyntaxShape, UntaggedValue, Value,
 };
 
-use super::utils::convert_columns;
+use super::utils::{convert_columns, parse_polars_error};
 
 pub struct DataFrame;
 
@@ -28,19 +28,19 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        select(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![Example {
             description: "Create new dataframe with column a",
-            example: "echo [[a b]; [1 2] [3 4]] | pls convert | pls select [a]",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls select [a]",
             result: None,
         }]
     }
 }
 
-fn select(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
@@ -55,14 +55,11 @@ fn select(args: CommandArgs) -> Result<OutputStream, ShellError> {
             &tag,
         )),
         Some(value) => {
-            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame {
-                dataframe: Some(ref df),
-                ..
-            })) = value.value
-            {
-                let res = df.select(&col_string).map_err(|e| {
-                    ShellError::labeled_error("Drop error", format!("{}", e), &col_span)
-                })?;
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                let res = df
+                    .as_ref()
+                    .select(&col_string)
+                    .map_err(|e| parse_polars_error::<&str>(&e, &col_span, None))?;
 
                 let value = Value {
                     value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(

crates/nu-command/src/commands/dataframe/show.rs

@@ -13,7 +13,7 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn usage(&self) -> &str {
-        "Show dataframe"
+        "Converts a section of the dataframe to a Table or List value"
     }
 
     fn signature(&self) -> Signature {
@@ -28,30 +28,30 @@ impl WholeStreamCommand for DataFrame {
     }
 
     fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
-        show(args)
+        command(args)
     }
 
     fn examples(&self) -> Vec<Example> {
         vec![
             Example {
                 description: "Shows head rows from dataframe",
-                example: "echo [[a b]; [1 2] [3 4]] | pls convert | pls show",
+                example: "[[a b]; [1 2] [3 4]] | pls convert | pls show",
                 result: None,
             },
             Example {
                 description: "Shows tail rows from dataframe",
-                example: "echo [[a b]; [1 2] [3 4] [5 6]] | pls convert | pls show -t -n 1",
+                example: "[[a b]; [1 2] [3 4] [5 6]] | pls convert | pls show -t -n 1",
                 result: None,
             },
         ]
     }
 }
 
-fn show(args: CommandArgs) -> Result<OutputStream, ShellError> {
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
     let tag = args.call_info.name_tag.clone();
     let mut args = args.evaluate_once()?;
 
-    let rows: Option<Tagged<usize>> = args.get_flag("rows")?;
+    let rows: Option<Tagged<usize>> = args.get_flag("n_rows")?;
     let tail: bool = args.has_flag("tail");
 
     match args.input.next() {

crates/nu-command/src/commands/dataframe/slice.rs

@@ -0,0 +1,74 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+use nu_source::Tagged;
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls slice"
+    }
+
+    fn usage(&self) -> &str {
+        "Creates new dataframe from a slice of rows"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls select")
+            .required("offset", SyntaxShape::Number, "start of slice")
+            .required("size", SyntaxShape::Number, "size of slice")
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Create new dataframe from a slice of the rows",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls slice 0 1",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+
+    let offset: Tagged<usize> = args.req(0)?;
+    let size: Tagged<usize> = args.req(1)?;
+
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                let res = df.as_ref().slice(offset.item as i64, size.item);
+
+                let value = Value {
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                    tag: tag.clone(),
+                };
+
+                Ok(OutputStream::one(value))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No dataframe in stream",
+                    "no dataframe found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}

crates/nu-command/src/commands/dataframe/tail.rs

@@ -0,0 +1,79 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    Signature, SyntaxShape, UntaggedValue, Value,
+};
+
+use nu_source::Tagged;
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls tail"
+    }
+
+    fn usage(&self) -> &str {
+        "Creates new dataframe with tail rows"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls select").optional(
+            "n_rows",
+            SyntaxShape::Number,
+            "Number of rows for tail",
+        )
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Create new dataframe with tail rows",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls tail",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+    let rows: Option<Tagged<usize>> = args.opt(0)?;
+
+    let rows = match rows {
+        Some(val) => val.item,
+        None => 5,
+    };
+
+    match args.input.next() {
+        None => Err(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag,
+        )),
+        Some(value) => {
+            if let UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) = value.value {
+                let res = df.as_ref().tail(Some(rows));
+
+                let value = Value {
+                    value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(
+                        res,
+                    ))),
+                    tag: tag.clone(),
+                };
+
+                Ok(OutputStream::one(value))
+            } else {
+                Err(ShellError::labeled_error(
+                    "No dataframe in stream",
+                    "no dataframe found in input stream",
+                    &tag,
+                ))
+            }
+        }
+    }
+}

crates/nu-command/src/commands/dataframe/to_csv.rs

@@ -0,0 +1,128 @@
+use std::fs::File;
+use std::path::PathBuf;
+
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::Primitive;
+use nu_protocol::Value;
+use nu_protocol::{dataframe::PolarsData, Signature, SyntaxShape, UntaggedValue};
+
+use polars::prelude::{CsvWriter, SerWriter};
+
+use nu_source::Tagged;
+
+use super::utils::parse_polars_error;
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls to_csv"
+    }
+
+    fn usage(&self) -> &str {
+        "Saves dataframe to csv file"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls to_csv")
+            .required("file", SyntaxShape::FilePath, "file path to save dataframe")
+            .named(
+                "delimiter",
+                SyntaxShape::String,
+                "file delimiter character",
+                Some('d'),
+            )
+            .switch("no_header", "Indicates if file doesn't have header", None)
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![
+            Example {
+                description: "Saves dataframe to csv file",
+                example: "[[a b]; [1 2] [3 4]] | pls convert | pls to_csv test.csv",
+                result: None,
+            },
+            Example {
+                description: "Saves dataframe to csv file using other delimiter",
+                example: "[[a b]; [1 2] [3 4]] | pls convert | pls to_csv test.csv -d '|'",
+                result: None,
+            },
+        ]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+    let file_name: Tagged<PathBuf> = args.req(0)?;
+    let delimiter: Option<Tagged<String>> = args.get_flag("delimiter")?;
+    let no_header: bool = args.has_flag("no_header");
+
+    let mut df = args
+        .input
+        .next()
+        .and_then(|value| match value.value {
+            UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) => Some(df),
+            _ => None,
+        })
+        .ok_or(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag.span,
+        ))?;
+
+    let mut file = File::create(&file_name.item).map_err(|e| {
+        ShellError::labeled_error(
+            "Error with file name",
+            format!("{}", e),
+            &file_name.tag.span,
+        )
+    })?;
+
+    let writer = CsvWriter::new(&mut file);
+
+    let writer = if no_header {
+        writer.has_headers(false)
+    } else {
+        writer.has_headers(true)
+    };
+
+    let writer = match delimiter {
+        None => writer,
+        Some(d) => {
+            if d.item.len() != 1 {
+                return Err(ShellError::labeled_error(
+                    "Incorrect delimiter",
+                    "Delimiter has to be one char",
+                    &d.tag,
+                ));
+            } else {
+                let delimiter = match d.item.chars().nth(0) {
+                    Some(d) => d as u8,
+                    None => unreachable!(),
+                };
+
+                writer.with_delimiter(delimiter)
+            }
+        }
+    };
+
+    writer
+        .finish(df.as_mut())
+        .map_err(|e| parse_polars_error::<&str>(&e, &file_name.tag.span, None))?;
+
+    let tagged_value = Value {
+        value: UntaggedValue::Primitive(Primitive::String(format!(
+            "saved {}",
+            &file_name.item.to_str().expect("csv file")
+        ))),
+        tag: Tag::unknown(),
+    };
+
+    Ok(InputStream::one(tagged_value).to_output_stream())
+}

crates/nu-command/src/commands/dataframe/to_parquet.rs

@@ -0,0 +1,85 @@
+use std::fs::File;
+use std::path::PathBuf;
+
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{dataframe::PolarsData, Primitive, Signature, SyntaxShape, UntaggedValue, Value};
+
+use polars::prelude::ParquetWriter;
+
+use nu_source::Tagged;
+
+use super::utils::parse_polars_error;
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls to_parquet"
+    }
+
+    fn usage(&self) -> &str {
+        "Saves dataframe to parquet file"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls to_parquet").required(
+            "file",
+            SyntaxShape::FilePath,
+            "file path to save dataframe",
+        )
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Saves dataframe to parquet file",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls to_parquet test.parquet",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let mut args = args.evaluate_once()?;
+    let file_name: Tagged<PathBuf> = args.req(0)?;
+
+    let mut df = args
+        .input
+        .next()
+        .and_then(|value| match value.value {
+            UntaggedValue::DataFrame(PolarsData::EagerDataFrame(df)) => Some(df),
+            _ => None,
+        })
+        .ok_or(ShellError::labeled_error(
+            "No input received",
+            "missing dataframe input from stream",
+            &tag.span,
+        ))?;
+
+    let file = File::create(&file_name.item).map_err(|e| {
+        ShellError::labeled_error(
+            "Error with file name",
+            format!("{}", e),
+            &file_name.tag.span,
+        )
+    })?;
+
+    ParquetWriter::new(file)
+        .finish(df.as_mut())
+        .map_err(|e| parse_polars_error::<&str>(&e, &file_name.tag.span, None))?;
+
+    let tagged_value = Value {
+        value: UntaggedValue::Primitive(Primitive::String(format!(
+            "saved {}",
+            &file_name.item.to_str().expect("parquet file")
+        ))),
+        tag: Tag::unknown(),
+    };
+
+    Ok(InputStream::one(tagged_value).to_output_stream())
+}

crates/nu-command/src/commands/dataframe/utils.rs

@@ -1,6 +1,7 @@
 use crate::prelude::*;
 use nu_errors::ShellError;
 use nu_protocol::{Primitive, UntaggedValue, Value};
+use polars::prelude::PolarsError;
 
 // Converts a Vec<Value> to a Vec<String> with a Span marking the whole
 // location of the columns for error referencing
@@ -40,3 +41,38 @@ pub(crate) fn convert_columns<'columns>(
 
     Ok((res, col_span))
 }
+
+pub(crate) fn parse_polars_error<T: AsRef<str>>(
+    e: &PolarsError,
+    span: &Span,
+    secondary: Option<T>,
+) -> ShellError {
+    let (msg, label) = match e {
+        PolarsError::PolarsArrowError(_) => ("PolarsArrow Error", format!("{}", e)),
+        PolarsError::ArrowError(_) => ("Arrow Error", format!("{}", e)),
+        PolarsError::InvalidOperation(_) => ("Invalid Operation", format!("{}", e)),
+        PolarsError::DataTypeMisMatch(_) => ("Data Type Mismatch", format!("{}", e)),
+        PolarsError::NotFound(_) => ("Not Found", format!("{}", e)),
+        PolarsError::ShapeMisMatch(_) => ("Shape Mismatch", format!("{}", e)),
+        PolarsError::Other(_) => ("Other", format!("{}", e)),
+        PolarsError::OutOfBounds(_) => ("Out Of Bounds", format!("{}", e)),
+        PolarsError::NoSlice => ("No Slice", format!("{}", e)),
+        PolarsError::NoData(_) => ("No Data", format!("{}", e)),
+        PolarsError::ValueError(_) => ("Value Error", format!("{}", e)),
+        PolarsError::MemoryNotAligned => ("Memory Not Aligned", format!("{}", e)),
+        PolarsError::ParquetError(_) => ("Parquet Error", format!("{}", e)),
+        PolarsError::RandError(_) => ("Rand Error", format!("{}", e)),
+        PolarsError::HasNullValues(_) => ("Has Null Values", format!("{}", e)),
+        PolarsError::UnknownSchema(_) => ("Unknown Schema", format!("{}", e)),
+        PolarsError::Various(_) => ("Various", format!("{}", e)),
+        PolarsError::Io(_) => ("Io Error", format!("{}", e)),
+        PolarsError::Regex(_) => ("Regex Error", format!("{}", e)),
+        PolarsError::Duplicate(_) => ("Duplicate Error", format!("{}", e)),
+        PolarsError::ImplementationError => ("Implementation Error", format!("{}", e)),
+    };
+
+    match secondary {
+        None => ShellError::labeled_error(msg, label, span),
+        Some(s) => ShellError::labeled_error_with_secondary(msg, label, span, s.as_ref(), span),
+    }
+}

crates/nu-command/src/commands/dataframe/where_.rs

@@ -0,0 +1,207 @@
+use crate::prelude::*;
+use nu_engine::{evaluate_baseline_expr, EvaluatedCommandArgs, WholeStreamCommand};
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{NuDataFrame, PolarsData},
+    hir::{CapturedBlock, ClassifiedCommand, Expression, Literal, Operator, SpannedExpression},
+    Primitive, Signature, SyntaxShape, UnspannedPathMember, UntaggedValue, Value,
+};
+
+use super::utils::parse_polars_error;
+use polars::prelude::{ChunkCompare, Series};
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "pls where"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("pls where").required(
+            "condition",
+            SyntaxShape::RowCondition,
+            "the condition that must match",
+        )
+    }
+
+    fn usage(&self) -> &str {
+        "Filter dataframe to match the condition"
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Filter dataframe based on column a",
+            example: "[[a b]; [1 2] [3 4]] | pls convert | pls where a == 1",
+            result: None,
+        }]
+    }
+}
+
+fn command(args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+    let args = args.evaluate_once()?;
+
+    let block: CapturedBlock = args.req(0)?;
+
+    let expression = block
+        .block
+        .block
+        .get(0)
+        .and_then(|group| {
+            group
+                .pipelines
+                .get(0)
+                .and_then(|v| v.list.get(0))
+                .and_then(|expr| match &expr {
+                    ClassifiedCommand::Expr(expr) => match &expr.as_ref().expr {
+                        Expression::Binary(expr) => Some(expr),
+                        _ => None,
+                    },
+                    _ => None,
+                })
+        })
+        .ok_or(ShellError::labeled_error(
+            "Expected a condition",
+            "expected a condition",
+            &tag.span,
+        ))?;
+
+    let lhs = match &expression.left.expr {
+        Expression::FullColumnPath(p) => p.as_ref().tail.get(0),
+        _ => None,
+    }
+    .ok_or(ShellError::labeled_error(
+        "No column name",
+        "Not a column name found in left hand side of comparison",
+        &expression.left.span,
+    ))?;
+
+    let (col_name, col_name_span) = match &lhs.unspanned {
+        UnspannedPathMember::String(name) => Ok((name, &lhs.span)),
+        _ => Err(ShellError::labeled_error(
+            "No column name",
+            "Not a string as column name",
+            &lhs.span,
+        )),
+    }?;
+
+    let rhs = evaluate_baseline_expr(&expression.right, &args.args.context)?;
+    let right_condition = match &rhs.value {
+        UntaggedValue::Primitive(primitive) => Ok(primitive),
+        _ => Err(ShellError::labeled_error(
+            "Incorrect argument",
+            "Expected primitive values",
+            &rhs.tag.span,
+        )),
+    }?;
+
+    filter_dataframe(
+        args,
+        &col_name,
+        &col_name_span,
+        &right_condition,
+        &expression.op,
+    )
+}
+
+macro_rules! comparison_arm {
+    ($comparison:expr,  $col:expr, $condition:expr, $span:expr) => {
+        match $condition {
+            Primitive::Int(val) => Ok($comparison($col, *val)),
+            Primitive::BigInt(val) => Ok($comparison(
+                $col,
+                val.to_i64()
+                    .expect("Internal error: protocol did not use compatible decimal"),
+            )),
+            Primitive::Decimal(val) => Ok($comparison(
+                $col,
+                val.to_f64()
+                    .expect("Internal error: protocol did not use compatible decimal"),
+            )),
+            Primitive::String(val) => {
+                let temp: &str = val.as_ref();
+                Ok($comparison($col, temp))
+            }
+            _ => Err(ShellError::labeled_error(
+                "Invalid datatype",
+                format!(
+                    "this operator cannot be used with the selected '{}' datatype",
+                    $col.dtype()
+                ),
+                &$span,
+            )),
+        }
+    };
+}
+
+// With the information extracted from the block we can filter the dataframe using
+// polars operations
+fn filter_dataframe(
+    mut args: EvaluatedCommandArgs,
+    col_name: &str,
+    col_name_span: &Span,
+    right_condition: &Primitive,
+    operator: &SpannedExpression,
+) -> Result<OutputStream, ShellError> {
+    let df = args
+        .input
+        .next()
+        .and_then(|value| match value.value {
+            UntaggedValue::DataFrame(PolarsData::EagerDataFrame(nu)) => Some(nu),
+            _ => None,
+        })
+        .ok_or(ShellError::labeled_error(
+            "Incorrect stream input",
+            "Expected dataframe in stream",
+            &args.call_info.name_tag.span,
+        ))?;
+
+    let col = df
+        .as_ref()
+        .column(col_name)
+        .map_err(|e| parse_polars_error::<&str>(&e, &col_name_span, None))?;
+
+    let op = match &operator.expr {
+        Expression::Literal(Literal::Operator(op)) => Ok(op),
+        _ => Err(ShellError::labeled_error(
+            "Incorrect argument",
+            "Expected operator",
+            &operator.span,
+        )),
+    }?;
+
+    let mask = match op {
+        Operator::Equal => comparison_arm!(Series::eq, col, right_condition, operator.span),
+        Operator::NotEqual => comparison_arm!(Series::neq, col, right_condition, operator.span),
+        Operator::LessThan => comparison_arm!(Series::lt, col, right_condition, operator.span),
+        Operator::LessThanOrEqual => {
+            comparison_arm!(Series::lt_eq, col, right_condition, operator.span)
+        }
+        Operator::GreaterThan => comparison_arm!(Series::gt, col, right_condition, operator.span),
+        Operator::GreaterThanOrEqual => {
+            comparison_arm!(Series::gt_eq, col, right_condition, operator.span)
+        }
+        _ => Err(ShellError::labeled_error(
+            "Incorrect operator",
+            "Not implemented operator for dataframes filter",
+            &operator.span,
+        )),
+    }?;
+
+    let res = df
+        .as_ref()
+        .filter(&mask)
+        .map_err(|e| parse_polars_error::<&str>(&e, &args.call_info.name_tag.span, None))?;
+
+    let value = Value {
+        value: UntaggedValue::DataFrame(PolarsData::EagerDataFrame(NuDataFrame::new(res))),
+        tag: args.call_info.name_tag.clone(),
+    };
+
+    Ok(OutputStream::one(value))
+}

crates/nu-command/src/commands/default_context.rs

@@ -278,6 +278,24 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             whole_stream_command(DataFrameSelect),
             #[cfg(feature = "dataframe")]
             whole_stream_command(DataFrameDTypes),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameDummies),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameHead),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameTail),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameSlice),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameMelt),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFramePivot),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameWhere),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameToParquet),
+            #[cfg(feature = "dataframe")]
+            whole_stream_command(DataFrameToCsv),
         ]);
 
         #[cfg(feature = "clipboard-cli")]

crates/nu-protocol/Cargo.toml

@@ -24,7 +24,15 @@ num-integer = "0.1.44"
 num-traits = "0.2.14"
 serde = { version = "1.0", features = ["derive"] }
 serde_bytes = "0.11.5"
-polars = {version = "0.13.4", optional = true}
+
+# implement conversions
+serde_json = "1.0"
+serde_yaml = "0.8.16"
+toml = "0.5.8"
+
+[dependencies.polars]
+version = "0.13.4"
+optional = true
 
 [features]
 dataframe = ["polars"]

crates/nu-protocol/src/dataframe/nu_dataframe.rs

@@ -46,15 +46,11 @@ type ColumnMap = HashMap<String, ColumnValues>;
 pub struct NuDataFrame {
     #[serde(skip_serializing)]
     pub dataframe: Option<DataFrame>,
-    pub name: String,
 }
 
 impl Default for NuDataFrame {
     fn default() -> Self {
-        NuDataFrame {
-            dataframe: None,
-            name: String::from("From Stream"),
-        }
+        NuDataFrame { dataframe: None }
     }
 }
 
@@ -62,14 +58,6 @@ impl NuDataFrame {
     pub fn new(df: polars::prelude::DataFrame) -> Self {
         NuDataFrame {
             dataframe: Some(df),
-            name: String::from("dataframe"),
-        }
-    }
-
-    pub fn new_with_name(df: polars::prelude::DataFrame, name: String) -> Self {
-        NuDataFrame {
-            dataframe: Some(df),
-            name,
         }
     }
 }
@@ -225,6 +213,24 @@ impl NuDataFrame {
     }
 }
 
+impl AsRef<polars::prelude::DataFrame> for NuDataFrame {
+    fn as_ref(&self) -> &polars::prelude::DataFrame {
+        match &self.dataframe {
+            Some(df) => df,
+            None => unreachable!("Accessing ref to dataframe from nu_dataframe"),
+        }
+    }
+}
+
+impl AsMut<polars::prelude::DataFrame> for NuDataFrame {
+    fn as_mut(&mut self) -> &mut polars::prelude::DataFrame {
+        match &mut self.dataframe {
+            Some(df) => df,
+            None => unreachable!("Accessing mut ref to dataframe from nu_dataframe"),
+        }
+    }
+}
+
 // Adds a separator to the vector of values using the column names from the
 // dataframe to create the Values Row
 fn add_separator(values: &mut Vec<Value>, df: &DataFrame) {
@@ -430,7 +436,6 @@ fn from_parsed_columns(column_values: ColumnMap, tag: &Tag) -> Result<NuDataFram
     match df {
         Ok(df) => Ok(NuDataFrame {
             dataframe: Some(df),
-            name: "From stream".to_string(),
         }),
         Err(e) => {
             return Err(ShellError::labeled_error(

crates/nu-protocol/src/dataframe/nu_groupby.rs

@@ -39,11 +39,6 @@ impl NuGroupBy {
     pub fn print(&self) -> Result<Vec<Value>, ShellError> {
         let mut values: Vec<Value> = Vec::new();
 
-        let mut data = TaggedDictBuilder::new(Tag::unknown());
-        data.insert_value("property", "dataframe");
-        data.insert_value("value", self.dataframe.name.as_ref());
-        values.push(data.into_value());
-
         let mut data = TaggedDictBuilder::new(Tag::unknown());
         data.insert_value("property", "group by");
         data.insert_value("value", self.by.join(", "));
@@ -52,3 +47,12 @@ impl NuGroupBy {
         Ok(values)
     }
 }
+
+impl AsRef<polars::prelude::DataFrame> for NuGroupBy {
+    fn as_ref(&self) -> &polars::prelude::DataFrame {
+        match &self.dataframe.dataframe {
+            Some(df) => df,
+            None => unreachable!("Accessing reference to dataframe from nu_groupby"),
+        }
+    }
+}

crates/nu-source/src/text.rs

@@ -11,9 +11,9 @@ use std::ops::Range;
 /// Used to represent the value of an input file.
 #[derive(Clone)]
 pub struct Text {
-    text: String,
-    start: usize,
-    end: usize,
+    pub text: String,
+    pub start: usize,
+    pub end: usize,
 }
 
 impl Text {