selected numeric data before correlation

doc/source/whatsnew/v0.22.0.txt

@@ -77,6 +77,7 @@ Other Enhancements
 - :func:`Series.fillna` now accepts a Series or a dict as a ``value`` for a categorical dtype (:issue:`17033`)
 - :func:`pandas.read_clipboard` updated to use qtpy, falling back to PyQt5 and then PyQt4, adding compatibility with Python3 and multiple python-qt bindings (:issue:`17722`)
 - Improved wording of ``ValueError`` raised in :func:`read_csv` when the ``usecols`` argument cannot match all columns. (:issue:`17301`)
+- :func:`DataFrame.corrwith` now silently drops non-numeric columns when passed a Series. Before, an exception was raised (:issue:`18570`).
 
 .. _whatsnew_0220.api_breaking:
 

pandas/core/frame.py

@@ -5577,7 +5577,7 @@ def corrwith(self, other, axis=0, drop=False):
 
         Parameters
         ----------
-        other : DataFrame
+        other : DataFrame, Series
         axis : {0 or 'index', 1 or 'columns'}, default 0
             0 or 'index' to compute column-wise, 1 or 'columns' for row-wise
         drop : boolean, default False
@@ -5588,10 +5588,11 @@ def corrwith(self, other, axis=0, drop=False):
         correls : Series
         """
         axis = self._get_axis_number(axis)
+        this = self._get_numeric_data()
+
         if isinstance(other, Series):
-            return self.apply(other.corr, axis=axis)
+            return this.apply(other.corr, axis=axis)
 
-        this = self._get_numeric_data()
         other = other._get_numeric_data()
 
         left, right = this.align(other, join='inner', copy=False)

pandas/tests/frame/test_analytics.py

@@ -240,6 +240,16 @@ def test_corrwith_matches_corrcoef(self):
         tm.assert_almost_equal(c1, c2)
         assert c1 < 1
 
+    def test_corrwith_mixed_dtypes(self):
+        # GH 18570
+        df = pd.DataFrame({'a': [1, 4, 3, 2], 'b': [4, 6, 7, 3],
+                           'c': ['a', 'b', 'c', 'd']})
+        s = pd.Series([0, 6, 7, 3])
+        result = df.corrwith(s)
+        corrs = [df['a'].corr(s), df['b'].corr(s)]
+        expected = pd.Series(data=corrs, index=['a', 'b'])
+        tm.assert_series_equal(result, expected)
+
     def test_bool_describe_in_mixed_frame(self):
         df = DataFrame({
             'string_data': ['a', 'b', 'c', 'd', 'e'],