matplotlib
diff --git a/‎doc/api/next_api_changes/2018-05-06-ZHD.rst
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+7Lines changed: 7 additions & 0 deletions b/‎doc/api/next_api_changes/2018-05-06-ZHD.rst
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+7Lines changed: 7 additions & 0 deletions
diff --git a/‎lib/matplotlib/axes/_axes.py
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+7-5Lines changed: 7 additions & 5 deletions b/‎lib/matplotlib/axes/_axes.py
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+7-5Lines changed: 7 additions & 5 deletions
diff --git a/‎lib/matplotlib/tests/test_mlab.py
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+2-2Lines changed: 2 additions & 2 deletions b/‎lib/matplotlib/tests/test_mlab.py
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+2-2Lines changed: 2 additions & 2 deletions
@@ -0,0 +1,7 @@
+Consistent handling of \*args in Axes.stem
+------------------------------------------
+
+:meth:`matplotlib.axex.Axes.stem` now raises TypeError when passed
+unhandled positional arguments.  If two or more arguments are passed
+(ie X, Y, [linefmt], ...) and Y cannot be cast to an array, an error
+will be raised instead of treating X as Y and Y as linefmt.
@@ -2350,17 +2350,19 @@ def stem(self, *args, linefmt=None, markerfmt=None, basefmt=None,
             which inspired this method.
 
         """
-        # Assume there's at least one data array
+        if not 1 <= len(args) <= 5:
+            raise TypeError('stem expected between 1 and 5 positional '
+                            'arguments, got {}'.format(args))
+
         y = np.asarray(args[0])
         args = args[1:]
 
         # Try a second one
-        try:
-            x, y = y, np.asarray(args[0], dtype=float)
-        except (IndexError, ValueError):
-            # The second array doesn't make sense, or it doesn't exist
+        if not args:
             x = np.arange(len(y))
         else:
+            x = y
+            y = np.asarray(args[0], dtype=float)
             args = args[1:]
 
         # defaults for formats
 
@@ -1119,7 +1119,7 @@ def test_detrend_detrend_linear_1d_slope_off_axis1(self):
         res = mlab.detrend(input, key=mlab.detrend_linear, axis=0)
         assert_allclose(res, targ, atol=self.atol)
 
-    def test_detrend_str_linear_2d_slope_off_axis0(self):
+    def test_detrend_str_linear_2d_slope_off_axis0_notranspose(self):
         arri = [self.sig_off,
                 self.sig_slope,
                 self.sig_slope + self.sig_off]
@@ -1131,7 +1131,7 @@ def test_detrend_str_linear_2d_slope_off_axis0(self):
         res = mlab.detrend(input, key='linear', axis=1)
         assert_allclose(res, targ, atol=self.atol)
 
-    def test_detrend_detrend_linear_1d_slope_off_axis1(self):
+    def test_detrend_detrend_linear_1d_slope_off_axis1_notranspose(self):
         arri = [self.sig_off,
                 self.sig_slope,
                 self.sig_slope + self.sig_off]