add eager cookbook

polars/polars-core/src/frame/groupby/pivot.rs

@@ -143,7 +143,7 @@ impl<'df, 'selection_str> GroupBy<'df, 'selection_str> {
     ///     let df = df!("foo" => &["A", "A", "B", "B", "C"],
     ///         "N" => &[1, 2, 2, 4, 2],
     ///         "bar" => &["k", "l", "m", "n", "0"]
-    ///         ).unwrap();
+    ///         )?;
     ///
     ///     df.groupby("foo")?
     ///     .pivot("bar", "N")

polars/polars-core/src/frame/groupby/resample.rs

@@ -50,7 +50,7 @@ impl DataFrame {
     /// use polars_core::frame::groupby::resample::SampleRule;
     ///
     /// fn example(df: &DataFrame) -> Result<DataFrame> {
-    ///     df.downsample("datetime", SampleRule::Minute(6))?
+    ///     df.downsample("datetime", SampleRule::Minute(5))?
     ///         .first()?
     ///         .sort("datetime", false)
     /// }

polars/polars-io/src/ipc.rs

@@ -42,6 +42,21 @@ use std::io::{Read, Seek, Write};
 use std::sync::Arc;
 
 /// Read Arrows IPC format into a DataFrame
+///
+/// # Example
+/// ```
+/// use polars_core::prelude::*;
+/// use std::fs::File;
+/// use polars_io::ipc::IpcReader;
+/// use polars_io::SerReader;
+///
+/// fn example() -> Result<DataFrame> {
+///     let file = File::open("file.ipc").expect("file not found");
+///
+///     IpcReader::new(file)
+///         .finish()
+/// }
+/// ```
 pub struct IpcReader<R> {
     /// File or Stream object
     reader: R,
@@ -85,6 +100,23 @@ where
 }
 
 /// Write a DataFrame to Arrow's IPC format
+///
+/// # Example
+///
+/// ```
+/// use polars_core::prelude::*;
+/// use polars_io::ipc::IpcWriter;
+/// use std::fs::File;
+/// use polars_io::SerWriter;
+///
+/// fn example(df: &mut DataFrame) -> Result<()> {
+///     let mut file = File::create("file.ipc").expect("could not create file");
+///
+///     IpcWriter::new(&mut file)
+///         .finish(df)
+/// }
+///
+/// ```
 pub struct IpcWriter<'a, W> {
     writer: &'a mut W,
 }

polars/polars-io/src/parquet.rs

@@ -149,6 +149,10 @@ where
 }
 
 /// Write a DataFrame to parquet format
+///
+/// # Example
+///
+///
 pub struct ParquetWriter<W> {
     writer: W,
 }