Add "median" operation (only for numbers)

Author: adamhooper

groupby.py

@@ -189,6 +189,7 @@ class Operation(Enum):
     NUNIQUE = "nunique"
     SUM = "sum"
     MEAN = "mean"
+    MEDIAN = "median"
     MIN = "min"
     MAX = "max"
     FIRST = "first"
@@ -197,7 +198,7 @@ def needs_column(self):
         return self != self.SIZE
 
     def needs_numeric_column(self):
-        return self in {self.SUM, self.MEAN}
+        return self in {self.SUM, self.MEAN, self.MEDIAN}
 
     def default_outname(self, colname):
         if self == self.SIZE:
@@ -207,6 +208,7 @@ def default_outname(self, colname):
             self.NUNIQUE: "Unique count",
             self.SUM: "Sum",
             self.MEAN: "Average",
+            self.MEDIAN: "Median",
             self.MIN: "Minimum",
             self.MAX: "Maximum",
             self.FIRST: "First",

test_groupby.py

@@ -318,6 +318,7 @@ def test_aggregate_numbers(self):
                 Aggregation(Operation.NUNIQUE, "B", "nunique"),
                 Aggregation(Operation.SUM, "B", "sum"),
                 Aggregation(Operation.MEAN, "B", "mean"),
+                Aggregation(Operation.MEDIAN, "B", "median"),
                 Aggregation(Operation.MIN, "B", "min"),
                 Aggregation(Operation.MAX, "B", "max"),
                 Aggregation(Operation.FIRST, "B", "first"),
@@ -332,6 +333,7 @@ def test_aggregate_numbers(self):
                     "nunique": [1, 2],
                     "sum": [2, 7],
                     "mean": [2, 7 / 3],
+                    "median": [2, 1],
                     "min": [2, 1],
                     "max": [2, 5],
                     "first": [2, 1],