DOC/TST : document and test negative width to bar

tacaswell · tacaswell · commit 96d2376746c3 · 2015-04-05T22:47:06.000-04:00
`ax.bar` allows you to specify the left edge of the bars.  The
'align' keyword allows the user to tell mpl to interpret the left
edges as the centers.  To use the left edges as the right edges the
user can simply pass a negative width.

 - Added note to the 'align' entry in the docstring
 - Added test to make sure this does not get 'fixed' with validation on
   width in bar
diff --git a/lib/matplotlib/axes/_axes.py b/lib/matplotlib/axes/_axes.py
@@ -1855,6 +1855,8 @@ def bar(self, left, height, width=0.8, bottom=None, **kwargs):
             If `edge`, aligns bars by their left edges (for vertical bars) and
             by their bottom edges (for horizontal bars). If `center`, interpret
             the `left` argument as the coordinates of the centers of the bars.
+            To align on the align bars on the right edge pass a negative
+            `width`.
 
         orientation : 'vertical' | 'horizontal', optional, default: 'vertical'
             The orientation of the bars.
diff --git a/lib/matplotlib/tests/test_axes.py b/lib/matplotlib/tests/test_axes.py
@@ -131,7 +131,7 @@ def test_twinx_cla():
 
 @image_comparison(baseline_images=["minorticks_on_rcParams_both"], extensions=['png'])
 def test_minorticks_on_rcParams_both():
-    
+
     fig = plt.figure()
     matplotlib.rcParams['xtick.minor.visible'] = True
     matplotlib.rcParams['ytick.minor.visible'] = True
@@ -3569,24 +3569,28 @@ def test_pathological_hexbin():
         fig.savefig(out)
         assert_equal(len(w), 0)
 
+
 @cleanup
 def test_color_None():
     # issue 3855
     fig, ax = plt.subplots()
     ax.plot([1,2], [1,2], color=None)
 
+
 @cleanup
 def test_color_alias():
     # issues 4157 and 4162
     fig, ax = plt.subplots()
     line = ax.plot([0, 1], c='lime')[0]
     assert_equal('lime', line.get_color())
 
+
 @cleanup
 def test_numerical_hist_label():
     fig, ax = plt.subplots()
     ax.hist([range(15)] * 5, label=range(5))
 
+
 @cleanup
 def test_move_offsetlabel():
     data = np.random.random(10) * 1e-22
@@ -3595,6 +3599,18 @@ def test_move_offsetlabel():
     ax.yaxis.tick_right()
     assert_equal((1, 0.5), ax.yaxis.offsetText.get_position())
 
+
+@cleanup
+def test_bar_negative_width():
+    fig, ax = plt.subplots()
+    res = ax.bar(range(1, 5), range(1, 5), width=-1)
+    assert_equal(len(res), 4)
+    for indx, b in enumerate(res):
+        assert_equal(b._x, indx)
+        assert_equal(b._width, 1)
+        assert_equal(b._height, indx + 1)
+
+
 if __name__ == '__main__':
     import nose
     import sys
