From 8dbbcc21d844e3e4261d063f94c2d77703633bf3 Mon Sep 17 00:00:00 2001
From: chielP <chielpeters@live.nl>
Date: Wed, 24 Jan 2024 16:07:17 +0100
Subject: [PATCH] cat casting

---
 .../chunked_array/logical/categorical/mod.rs  | 21 +++++++++++++++++++
 .../tests/unit/datatypes/test_categorical.py  | 12 +++++++++++
 2 files changed, 33 insertions(+)

diff --git a/crates/polars-core/src/chunked_array/logical/categorical/mod.rs b/crates/polars-core/src/chunked_array/logical/categorical/mod.rs
index 9d79dc28de8a9..7eaec38f72016 100644
--- a/crates/polars-core/src/chunked_array/logical/categorical/mod.rs
+++ b/crates/polars-core/src/chunked_array/logical/categorical/mod.rs
@@ -355,6 +355,27 @@ impl LogicalType for CategoricalChunked {
                 // Otherwise we do nothing
                 Ok(self.clone().set_ordering(*ordering, true).into_series())
             },
+            dt if dt.is_numeric() => {
+                // Apply the cast to to the categories and then index into the casted series
+                let categories =
+                    StringChunked::with_chunk("", self.get_rev_map().get_categories().clone());
+                let casted_series = categories.cast(dtype)?;
+
+                macro_rules! get_elements {
+                    ($ca:expr) => {{
+                        Ok(self
+                            .physical()
+                            .into_iter()
+                            .map(|opt_el| {
+                                opt_el.map(|el: u32| unsafe {
+                                    $ca.get_unchecked(el as usize).unwrap()
+                                })
+                            })
+                            .collect())
+                    }};
+                }
+                downcast_as_macro_arg_physical!(casted_series, get_elements)
+            },
             _ => self.physical.cast(dtype),
         }
     }
diff --git a/py-polars/tests/unit/datatypes/test_categorical.py b/py-polars/tests/unit/datatypes/test_categorical.py
index 07f7a20263059..4e02decb8fe9f 100644
--- a/py-polars/tests/unit/datatypes/test_categorical.py
+++ b/py-polars/tests/unit/datatypes/test_categorical.py
@@ -800,3 +800,15 @@ def test_sort_categorical_retain_none(
                 "foo",
                 "ham",
             ]
+
+
+def test_cast_from_cat_to_numeric() -> None:
+    cat_series = pl.Series(
+        "cat_series",
+        ["0.69845702", "0.69317475", "2.43642724", "-0.95303469", "0.60684237"],
+    ).cast(pl.Categorical)
+    maximum = cat_series.cast(pl.Float32).max()
+    assert abs(maximum - 2.43642724) < 1e-6  # type: ignore[operator]
+
+    s = pl.Series(["1", "2", "3"], dtype=pl.Categorical)
+    assert s.cast(pl.UInt8).sum() == 6