ueshin commented on a change in pull request #33625:
URL: https://github.com/apache/spark/pull/33625#discussion_r684421935
##########
File path: python/pyspark/pandas/frame.py
##########
@@ -3459,6 +3458,111 @@ def mask(
cond_inversed = cond._apply_series_op(lambda psser: ~psser)
return self.where(cond_inversed, other)
+ # TODO: Support axis as 1 or 'columns'
+ def mode(
+ self, axis: Union[int, str] = 0, numeric_only: bool = False, dropna:
bool = True
Review comment:
nit: `Axis` instead of `Union[int, str]`?
##########
File path: python/pyspark/pandas/frame.py
##########
@@ -3459,6 +3458,111 @@ def mask(
cond_inversed = cond._apply_series_op(lambda psser: ~psser)
return self.where(cond_inversed, other)
+ # TODO: Support axis as 1 or 'columns'
+ def mode(
+ self, axis: Union[int, str] = 0, numeric_only: bool = False, dropna:
bool = True
+ ) -> "DataFrame":
+ """
+ Get the mode(s) of each element along the selected axis.
+
+ The mode of a set of values is the value that appears most often.
+ It can be multiple values.
+
+ Parameters
+ ----------
+ axis : {0 or 'index', 1 or 'columns'}, default 0
+ The axis to iterate over while searching for the mode:
+ * 0 or 'index' : get mode of each column
+ * 1 or 'columns' : get mode of each row.
+
+ numeric_only : bool, default False
+ If True, only apply to numeric columns.
+
+ dropna : bool, default True
+ Don't consider counts of NaN/NaT.
+
+ Returns
+ -------
+ DataFrame
+ The modes of each column or row.
+
+ See Also
+ --------
+ Series.mode : Return the highest frequency value in a Series.
+ Series.value_counts : Return the counts of values in a Series.
+
+ Examples
+ --------
+ >>> psdf = ps.DataFrame(
+ ... [("bird", 2, 2), ("mammal", 4, np.nan), ("arthropod", 8, 0),
("bird", 2, np.nan)],
+ ... index=("falcon", "horse", "spider", "ostrich"),
+ ... columns=("species", "legs", "wings"),
+ ... )
+ >>> psdf
+ species legs wings
+ falcon bird 2 2.0
+ horse mammal 4 NaN
+ spider arthropod 8 0.0
+ ostrich bird 2 NaN
+
+ >>> psdf.mode() # doctest: +SKIP
+ species legs wings
+ 0 bird 2.0 0.0
+ 1 None NaN 2.0
+
+ >>> psdf.mode(dropna=False)
+ species legs wings
+ 0 bird 2 NaN
+
+ >>> psdf.mode(numeric_only=True) # doctest: +SKIP
+ legs wings
+ 0 2.0 0.0
+ 1 NaN 2.0
+
+ Notes
+ -----
+ The current implementation of mode requires joins multiple times
+ (columns count - 1 times when axis is 0 or 'index'), which is
potentially expensive.
+
+ The order of multiple modes (within each column when axis is 0 or
'index') is undetermined.
Review comment:
I guess this section should be above the `Example` section. (should be
above the `Parameters` section?)
##########
File path: python/pyspark/pandas/tests/test_dataframe.py
##########
@@ -1900,6 +1900,29 @@ def test_isin(self):
with self.assertRaisesRegex(TypeError, msg):
psdf.isin(1)
+ def test_mode(self):
+ pdf = pd.DataFrame(
+ [("bird", 2, 2), ("mammal", 4, 0), ("arthropod", 8, 0), ("bird",
2, np.nan)],
+ index=("falcon", "horse", "spider", "ostrich"),
+ columns=("species", "legs", "wings"),
+ )
+ psdf = ps.from_pandas(pdf)
+ self.assert_eq(
+ psdf.mode(),
+ pdf.mode(),
+ )
+ self.assert_eq(
+ psdf.mode(numeric_only=True),
+ pdf.mode(numeric_only=True),
+ )
Review comment:
Could you add tests with `pdf[[]].mode()`?
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