describe command (#3907)

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

@@ -0,0 +1,232 @@
+use crate::prelude::*;
+use nu_engine::WholeStreamCommand;
+use nu_errors::ShellError;
+use nu_protocol::{
+    dataframe::{Column, NuDataFrame},
+    Signature, UntaggedValue,
+};
+use polars::{
+    chunked_array::ChunkedArray,
+    prelude::{
+        AnyValue, DataFrame as PolarsDF, DataType, Float64Type, IntoSeries, NewChunkedArray,
+        Series, Utf8Type,
+    },
+};
+
+use super::utils::parse_polars_error;
+
+pub struct DataFrame;
+
+impl WholeStreamCommand for DataFrame {
+    fn name(&self) -> &str {
+        "dataframe describe"
+    }
+
+    fn usage(&self) -> &str {
+        "[DataFrame] Describes dataframes numeric columns"
+    }
+
+    fn signature(&self) -> Signature {
+        Signature::build("dataframe describe")
+    }
+
+    fn run(&self, args: CommandArgs) -> Result<OutputStream, ShellError> {
+        command(args)
+    }
+
+    fn examples(&self) -> Vec<Example> {
+        vec![Example {
+            description: "Describes dataframe",
+            example: "[[a b]; [1 1] [1 1]] | dataframe to-df | dataframe describe",
+            result: Some(vec![NuDataFrame::try_from_columns(
+                vec![
+                    Column::new(
+                        "descriptor".to_string(),
+                        vec![
+                            UntaggedValue::string("count").into(),
+                            UntaggedValue::string("sum").into(),
+                            UntaggedValue::string("mean").into(),
+                            UntaggedValue::string("median").into(),
+                            UntaggedValue::string("std").into(),
+                            UntaggedValue::string("min").into(),
+                            UntaggedValue::string("25%").into(),
+                            UntaggedValue::string("50%").into(),
+                            UntaggedValue::string("75%").into(),
+                            UntaggedValue::string("max").into(),
+                        ],
+                    ),
+                    Column::new(
+                        "a (i64)".to_string(),
+                        vec![
+                            UntaggedValue::decimal_from_float(2.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(2.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(0.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                        ],
+                    ),
+                    Column::new(
+                        "b (i64)".to_string(),
+                        vec![
+                            UntaggedValue::decimal_from_float(2.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(2.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(0.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                            UntaggedValue::decimal_from_float(1.0, Span::default()).into(),
+                        ],
+                    ),
+                ],
+                &Span::default(),
+            )
+            .expect("simple df for test should not fail")
+            .into_value(Tag::default())]),
+        }]
+    }
+}
+
+fn command(mut args: CommandArgs) -> Result<OutputStream, ShellError> {
+    let tag = args.call_info.name_tag.clone();
+
+    let (df, _) = NuDataFrame::try_from_stream(&mut args.input, &tag.span)?;
+
+    let names = ChunkedArray::<Utf8Type>::new_from_opt_slice(
+        "descriptor",
+        &[
+            Some("count"),
+            Some("sum"),
+            Some("mean"),
+            Some("median"),
+            Some("std"),
+            Some("min"),
+            Some("25%"),
+            Some("50%"),
+            Some("75%"),
+            Some("max"),
+        ],
+    )
+    .into_series();
+
+    let head = std::iter::once(names);
+
+    let tail = df.as_ref().get_columns().iter().map(|col| {
+        let count = col.len() as f64;
+
+        let sum = match col.sum_as_series().cast_with_dtype(&DataType::Float64) {
+            Ok(ca) => match ca.get(0) {
+                AnyValue::Float64(v) => Some(v),
+                _ => None,
+            },
+            Err(_) => None,
+        };
+
+        let mean = match col.mean_as_series().get(0) {
+            AnyValue::Float64(v) => Some(v),
+            _ => None,
+        };
+
+        let median = match col.median_as_series().get(0) {
+            AnyValue::Float64(v) => Some(v),
+            _ => None,
+        };
+
+        let std = match col.std_as_series().get(0) {
+            AnyValue::Float64(v) => Some(v),
+            _ => None,
+        };
+
+        let min = match col.min_as_series().cast_with_dtype(&DataType::Float64) {
+            Ok(ca) => match ca.get(0) {
+                AnyValue::Float64(v) => Some(v),
+                _ => None,
+            },
+            Err(_) => None,
+        };
+
+        let q_25 = match col.quantile_as_series(0.25) {
+            Ok(ca) => match ca.cast_with_dtype(&DataType::Float64) {
+                Ok(ca) => match ca.get(0) {
+                    AnyValue::Float64(v) => Some(v),
+                    _ => None,
+                },
+                Err(_) => None,
+            },
+            Err(_) => None,
+        };
+
+        let q_50 = match col.quantile_as_series(0.50) {
+            Ok(ca) => match ca.cast_with_dtype(&DataType::Float64) {
+                Ok(ca) => match ca.get(0) {
+                    AnyValue::Float64(v) => Some(v),
+                    _ => None,
+                },
+                Err(_) => None,
+            },
+            Err(_) => None,
+        };
+
+        let q_75 = match col.quantile_as_series(0.75) {
+            Ok(ca) => match ca.cast_with_dtype(&DataType::Float64) {
+                Ok(ca) => match ca.get(0) {
+                    AnyValue::Float64(v) => Some(v),
+                    _ => None,
+                },
+                Err(_) => None,
+            },
+            Err(_) => None,
+        };
+
+        let max = match col.max_as_series().cast_with_dtype(&DataType::Float64) {
+            Ok(ca) => match ca.get(0) {
+                AnyValue::Float64(v) => Some(v),
+                _ => None,
+            },
+            Err(_) => None,
+        };
+
+        let name = format!("{} ({})", col.name(), col.dtype());
+        ChunkedArray::<Float64Type>::new_from_opt_slice(
+            name.as_str(),
+            &[
+                Some(count),
+                sum,
+                mean,
+                median,
+                std,
+                min,
+                q_25,
+                q_50,
+                q_75,
+                max,
+            ],
+        )
+        .into_series()
+    });
+
+    let res = head.chain(tail).collect::<Vec<Series>>();
+    let df = PolarsDF::new(res).map_err(|e| parse_polars_error::<&str>(&e, &tag.span, None))?;
+    let df = NuDataFrame::dataframe_to_value(df, tag);
+    Ok(OutputStream::one(df))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::DataFrame;
+    use super::ShellError;
+
+    #[test]
+    fn examples_work_as_expected() -> Result<(), ShellError> {
+        use crate::examples::test_dataframe as test_examples;
+
+        test_examples(DataFrame {})
+    }
+}

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

@@ -2,6 +2,7 @@ pub mod aggregate;
 pub mod append;
 pub mod column;
 pub mod command;
+pub mod describe;
 pub mod drop;
 pub mod drop_duplicates;
 pub mod drop_nulls;
@@ -35,6 +36,7 @@ pub use aggregate::DataFrame as DataFrameAggregate;
 pub use append::DataFrame as DataFrameAppend;
 pub use column::DataFrame as DataFrameColumn;
 pub use command::Command as DataFrame;
+pub use describe::DataFrame as DataFrameDescribe;
 pub use drop::DataFrame as DataFrameDrop;
 pub use drop_duplicates::DataFrame as DataFrameDropDuplicates;
 pub use drop_nulls::DataFrame as DataFrameDropNulls;

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

@@ -27,19 +27,19 @@ pub use core_commands::*;
 pub use dataframe::{
     DataFrame, DataFrameAggregate, DataFrameAllFalse, DataFrameAllTrue, DataFrameAppend,
     DataFrameArgMax, DataFrameArgMin, DataFrameArgSort, DataFrameArgTrue, DataFrameArgUnique,
-    DataFrameColumn, DataFrameConcatenate, DataFrameContains, DataFrameDTypes, DataFrameDrop,
-    DataFrameDropDuplicates, DataFrameDropNulls, DataFrameDummies, DataFrameFilter, DataFrameFirst,
-    DataFrameGet, DataFrameGetDay, DataFrameGetHour, DataFrameGetMinute, DataFrameGetMonth,
-    DataFrameGetNanoSecond, DataFrameGetOrdinal, DataFrameGetSecond, DataFrameGetWeek,
-    DataFrameGetWeekDay, DataFrameGetYear, DataFrameGroupBy, DataFrameIsDuplicated, DataFrameIsIn,
-    DataFrameIsNotNull, DataFrameIsNull, DataFrameIsUnique, DataFrameJoin, DataFrameLast,
-    DataFrameList, DataFrameMelt, DataFrameNNull, DataFrameNUnique, DataFrameNot, DataFrameOpen,
-    DataFramePivot, DataFrameReplace, DataFrameReplaceAll, DataFrameSample, DataFrameSelect,
-    DataFrameSeriesRename, DataFrameSet, DataFrameSetWithIdx, DataFrameShape, DataFrameShift,
-    DataFrameShow, DataFrameSlice, DataFrameSort, DataFrameStrFTime, DataFrameStringLengths,
-    DataFrameStringSlice, DataFrameTake, DataFrameToCsv, DataFrameToDF, DataFrameToLowercase,
-    DataFrameToParquet, DataFrameToUppercase, DataFrameUnique, DataFrameValueCounts,
-    DataFrameWhere, DataFrameWithColumn,
+    DataFrameColumn, DataFrameConcatenate, DataFrameContains, DataFrameDTypes, DataFrameDescribe,
+    DataFrameDrop, DataFrameDropDuplicates, DataFrameDropNulls, DataFrameDummies, DataFrameFilter,
+    DataFrameFirst, DataFrameGet, DataFrameGetDay, DataFrameGetHour, DataFrameGetMinute,
+    DataFrameGetMonth, DataFrameGetNanoSecond, DataFrameGetOrdinal, DataFrameGetSecond,
+    DataFrameGetWeek, DataFrameGetWeekDay, DataFrameGetYear, DataFrameGroupBy,
+    DataFrameIsDuplicated, DataFrameIsIn, DataFrameIsNotNull, DataFrameIsNull, DataFrameIsUnique,
+    DataFrameJoin, DataFrameLast, DataFrameList, DataFrameMelt, DataFrameNNull, DataFrameNUnique,
+    DataFrameNot, DataFrameOpen, DataFramePivot, DataFrameReplace, DataFrameReplaceAll,
+    DataFrameSample, DataFrameSelect, DataFrameSeriesRename, DataFrameSet, DataFrameSetWithIdx,
+    DataFrameShape, DataFrameShift, DataFrameShow, DataFrameSlice, DataFrameSort,
+    DataFrameStrFTime, DataFrameStringLengths, DataFrameStringSlice, DataFrameTake, DataFrameToCsv,
+    DataFrameToDF, DataFrameToLowercase, DataFrameToParquet, DataFrameToUppercase, DataFrameUnique,
+    DataFrameValueCounts, DataFrameWhere, DataFrameWithColumn,
 };
 pub use env::*;
 pub use filesystem::*;

crates/nu-command/src/default_context.rs

@@ -340,6 +340,7 @@ pub fn create_default_context(interactive: bool) -> Result<EvaluationContext, Bo
             whole_stream_command(DataFrameGetOrdinal),
             whole_stream_command(DataFrameGetNanoSecond),
             whole_stream_command(DataFrameStrFTime),
+            whole_stream_command(DataFrameDescribe),
         ]);
 
         #[cfg(feature = "clipboard-cli")]