Merge pull request matplotlib#1675 from megies/errorbar_alpha

fix "alpha" kwarg in errorbar plot

Author: dmcdougall

lib/matplotlib/axes.py

@@ -5441,6 +5441,8 @@ def errorbar(self, x, y, yerr=None, xerr=None,
                 lines_kw['lw']=kwargs['lw']
         if 'transform' in kwargs:
             lines_kw['transform'] = kwargs['transform']
+        if 'alpha' in kwargs:
+            lines_kw['alpha'] = kwargs['alpha']
         if 'zorder' in kwargs:
             lines_kw['zorder'] = kwargs['zorder']
 
@@ -5491,6 +5493,8 @@ def xywhere(xs, ys, mask):
                 plot_kw['mew']=kwargs['mew']
             if 'transform' in kwargs:
                 plot_kw['transform'] = kwargs['transform']
+            if 'alpha' in kwargs:
+                plot_kw['alpha'] = kwargs['alpha']
             if 'zorder' in kwargs:
                 plot_kw['zorder'] = kwargs['zorder']
 

lib/matplotlib/tests/baseline_images/test_axes/errorbar_mixed.pdf

@@ -900,8 +900,8 @@ def test_errorbar():
     ax.locator_params(nbins=4)
 
     ax = axs[0,1]
-    ax.errorbar(x, y, xerr=xerr, fmt='o')
-    ax.set_title('Hor. symmetric')
+    ax.errorbar(x, y, xerr=xerr, fmt='o', alpha=0.4)
+    ax.set_title('Hor. symmetric w/ alpha')
 
     ax = axs[1,0]
     ax.errorbar(x, y, yerr=[yerr, 2*yerr], xerr=[xerr, 2*xerr], fmt='--o')