catch too-negative values

Author: jbrockmendel

pandas/compat/numpy/function.py

@@ -376,6 +376,8 @@ def validate_minmax_axis(axis):
     ValueError
     """
     ndim = 1  # hard-coded for Index
-    if axis is not None and axis >= ndim:
+    if axis is None:
+        return
+    if axis >= ndim or (axis < 0 and ndim - axis < 0):
         raise ValueError("`axis` must be fewer than the number of "
                          "dimensions ({ndim})".format(ndim=ndim))

pandas/tests/indexes/datetimelike.py

@@ -15,6 +15,10 @@ def test_argmax_axis_invalid(self):
             rng.argmax(axis=1)
         with pytest.raises(ValueError):
             rng.argmin(axis=2)
+        with pytest.raises(ValueError):
+            rng.min(axis=-2)
+        with pytest.raises(ValueError):
+            rng.max(axis=-3)
 
     def test_can_hold_identifiers(self):
         idx = self.create_index()