Add rust examples for time-series resampling and timezones

docs/src/rust/user-guide/transformations/time-series/resampling.rs

@@ -0,0 +1,43 @@
+// --8<-- [start:setup]
+use chrono::prelude::*;
+use polars::io::prelude::*;
+use polars::prelude::*;
+use polars::time::prelude::*;
+// --8<-- [end:setup]
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // --8<-- [start:df]
+    let df = df!(
+    "time" => date_range(
+        "time",
+        NaiveDate::from_ymd_opt(2021, 12, 16).unwrap().and_hms_opt(0, 0, 0).unwrap(),
+        NaiveDate::from_ymd_opt(2021, 12, 16).unwrap().and_hms_opt(3, 0, 0).unwrap(),
+        Duration::parse("30m"),
+        ClosedWindow::Both,
+        TimeUnit::Milliseconds, None)?,
+        "groups" => &["a", "a", "a", "b", "b", "a", "a"],
+        "values" => &[1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0],
+    )?;
+    println!("{}", &df);
+    // --8<-- [end:df]
+
+    // --8<-- [start:upsample]
+    let out1 = df
+        .clone()
+        .upsample::<[String; 0]>([], "time", Duration::parse("15m"), Duration::parse("0"))?
+        .fill_null(FillNullStrategy::Forward(None))?;
+    println!("{}", &out1);
+    // --8<-- [end:upsample]
+
+    // --8<-- [start:upsample2]
+    let out2 = df
+        .clone()
+        .upsample::<[String; 0]>([], "time", Duration::parse("15m"), Duration::parse("0"))?
+        .lazy()
+        .with_columns([col("values").interpolate(InterpolationMethod::Linear)])
+        .collect()?
+        .fill_null(FillNullStrategy::Forward(None))?;
+    println!("{}", &out2);
+    // --8<-- [end:upsample2]
+    Ok(())
+}

docs/src/rust/user-guide/transformations/time-series/timezones.rs

@@ -0,0 +1,46 @@
+// --8<-- [start:setup]
+use polars::prelude::*;
+// --8<-- [end:setup]
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    // --8<-- [start:example]
+    let ts = ["2021-03-27 03:00", "2021-03-28 03:00"];
+    let tz_naive = Series::new("tz_naive", &ts);
+    let time_zones_df = DataFrame::new(vec![tz_naive])?
+        .lazy()
+        .select([col("tz_naive").str().strptime(
+            DataType::Datetime(TimeUnit::Milliseconds, None),
+            StrptimeOptions::default(),
+        )])
+        .with_columns([col("tz_naive")
+            .dt()
+            .replace_time_zone(Some("UTC".to_string()), None)
+            .alias("tz_aware")])
+        .collect()?;
+
+    println!("{}", &time_zones_df);
+    // --8<-- [end:example]
+
+    // --8<-- [start:example2]
+    let time_zones_operations = time_zones_df
+        .lazy()
+        .select([
+            col("tz_aware")
+                .dt()
+                .replace_time_zone(Some("Europe/Brussels".to_string()), None)
+                .alias("replace time zone"),
+            col("tz_aware")
+                .dt()
+                .convert_time_zone("Asia/Kathmandu".to_string())
+                .alias("convert time zone"),
+            col("tz_aware")
+                .dt()
+                .replace_time_zone(None, None)
+                .alias("unset time zone"),
+        ])
+        .collect()?;
+    println!("{}", &time_zones_operations);
+    // --8<-- [end:example2]
+
+    Ok(())
+}