fix rank empty schema

pola-rs · Dec 5, 2021 · 2091863 · 2091863
1 parent ae2aad5
commit 2091863
Showing 1 changed file with 22 additions and 5 deletions.
diff --git a/polars/polars-core/src/chunked_array/ops/unique/rank.rs b/polars/polars-core/src/chunked_array/ops/unique/rank.rs
@@ -17,11 +17,20 @@ pub enum RankMethod {
 }
 
 pub(crate) fn rank(s: &Series, method: RankMethod) -> Series {
-    if s.len() == 1 {
-        return match method {
-            Average => Series::new(s.name(), &[1.0f32]),
-            _ => Series::new(s.name(), &[1u32]),
-        };
+    match s.len() {
+        1 => {
+            return match method {
+                Average => Series::new(s.name(), &[1.0f32]),
+                _ => Series::new(s.name(), &[1u32]),
+            };
+        }
+        0 => {
+            return match method {
+                Average => Float32Chunked::new_from_slice(s.name(), &[]).into_series(),
+                _ => UInt32Chunked::new_from_slice(s.name(), &[]).into_series(),
+            }
+        }
+        _ => {}
     }
     // don't fully understand how to deal with nulls yet
     // impute with the maximum value possible.
@@ -337,4 +346,12 @@ mod test {
         let out = rank(&s, RankMethod::Max);
         assert_eq!(out.dtype(), &DataType::UInt32);
     }
+    #[test]
+    fn test_rank_empty() {
+        let s = UInt32Chunked::new_from_slice("", &[]).into_series();
+        let out = rank(&s, RankMethod::Average);
+        assert_eq!(out.dtype(), &DataType::Float32);
+        let out = rank(&s, RankMethod::Max);
+        assert_eq!(out.dtype(), &DataType::UInt32);
+    }
 }