BUG: clip should handle null values

closes pandas-dev#17276

Author: Michael Gasvoda <mgasvoda@mercatus.gmu.edu>
Author: mgasvoda <mgasvoda01@gmail.com>

Closes pandas-dev#17288 from mgasvoda/master and squashes the following commits:

a1dbdf2 [mgasvoda] Merge branch 'master' into master
9333952 [Michael Gasvoda] Checking output of tests
4e0464e [Michael Gasvoda] fixing whatsnew text
c442040 [Michael Gasvoda] formatting fixes
7e23678 [Michael Gasvoda] formatting updates
781ea72 [Michael Gasvoda] whatsnew entry
d9627fe [Michael Gasvoda] adding clip tests
9aa0159 [Michael Gasvoda] Treating na values as none for clips

doc/source/whatsnew/v0.21.0.txt

@@ -132,7 +132,6 @@ Other Enhancements
 
 
 
-
 .. _whatsnew_0210.api_breaking:
 
 Backwards incompatible API changes
@@ -384,6 +383,7 @@ Reshaping
 Numeric
 ^^^^^^^
 - Bug in ``.clip()`` with ``axis=1`` and a list-like for ``threshold`` is passed; previously this raised ``ValueError`` (:issue:`15390`)
+- :func:`Series.clip()` and :func:`DataFrame.clip()` now treat NA values for upper and lower arguments as ``None`` instead of raising ``ValueError`` (:issue:`17276`).
 
 
 Categorical

pandas/core/generic.py

@@ -4741,9 +4741,6 @@ def _clip_with_one_bound(self, threshold, method, axis, inplace):
         if axis is not None:
             axis = self._get_axis_number(axis)
 
-        if np.any(isna(threshold)):
-            raise ValueError("Cannot use an NA value as a clip threshold")
-
         # method is self.le for upper bound and self.ge for lower bound
         if is_scalar(threshold) and is_number(threshold):
             if method.__name__ == 'le':
@@ -4823,6 +4820,14 @@ def clip(self, lower=None, upper=None, axis=None, inplace=False,
 
         axis = nv.validate_clip_with_axis(axis, args, kwargs)
 
+        # GH 17276
+        # numpy doesn't like NaN as a clip value
+        # so ignore
+        if np.any(pd.isnull(lower)):
+            lower = None
+        if np.any(pd.isnull(upper)):
+            upper = None
+
         # GH 2747 (arguments were reversed)
         if lower is not None and upper is not None:
             if is_scalar(lower) and is_scalar(upper):
@@ -4839,7 +4844,6 @@ def clip(self, lower=None, upper=None, axis=None, inplace=False,
         if upper is not None:
             if inplace:
                 result = self
-
             result = result.clip_upper(upper, axis, inplace=inplace)
 
         return result

pandas/tests/frame/test_analytics.py

@@ -1931,22 +1931,16 @@ def test_clip_against_frame(self, axis):
         tm.assert_frame_equal(clipped_df[ub_mask], ub[ub_mask])
         tm.assert_frame_equal(clipped_df[mask], df[mask])
 
-    def test_clip_na(self):
-        msg = "Cannot use an NA"
-        with tm.assert_raises_regex(ValueError, msg):
-            self.frame.clip(lower=np.nan)
-
-        with tm.assert_raises_regex(ValueError, msg):
-            self.frame.clip(lower=[np.nan])
-
-        with tm.assert_raises_regex(ValueError, msg):
-            self.frame.clip(upper=np.nan)
-
-        with tm.assert_raises_regex(ValueError, msg):
-            self.frame.clip(upper=[np.nan])
-
-        with tm.assert_raises_regex(ValueError, msg):
-            self.frame.clip(lower=np.nan, upper=np.nan)
+    def test_clip_with_na_args(self):
+        """Should process np.nan argument as None """
+        # GH # 17276
+        tm.assert_frame_equal(self.frame.clip(np.nan), self.frame)
+        tm.assert_frame_equal(self.frame.clip(upper=[1, 2, np.nan]),
+                              self.frame)
+        tm.assert_frame_equal(self.frame.clip(lower=[1, np.nan, 3]),
+                              self.frame)
+        tm.assert_frame_equal(self.frame.clip(upper=np.nan, lower=np.nan),
+                              self.frame)
 
     # Matrix-like
 

pandas/tests/series/test_analytics.py

@@ -1000,6 +1000,17 @@ def test_clip_types_and_nulls(self):
             assert list(isna(s)) == list(isna(l))
             assert list(isna(s)) == list(isna(u))
 
+    def test_clip_with_na_args(self):
+        """Should process np.nan argument as None """
+        # GH # 17276
+        s = Series([1, 2, 3])
+
+        assert_series_equal(s.clip(np.nan), Series([1, 2, 3]))
+        assert_series_equal(s.clip(upper=[1, 1, np.nan]), Series([1, 2, 3]))
+        assert_series_equal(s.clip(lower=[1, np.nan, 1]), Series([1, 2, 3]))
+        assert_series_equal(s.clip(upper=np.nan, lower=np.nan),
+                            Series([1, 2, 3]))
+
     def test_clip_against_series(self):
         # GH #6966