Fixes an error in the documentation, '-.' line style is documented as

dylan-evans · dylan-evans · commit ac819f49ecfe · 2016-02-29T16:24:34.000+10:00
'dash_dot' but is 'dashdot' in code.
diff --git a/lib/matplotlib/collections.py b/lib/matplotlib/collections.py
@@ -510,7 +510,7 @@ def set_linestyle(self, ls):
         ===========================   =================
         ``'-'`` or ``'solid'``        solid line
         ``'--'`` or  ``'dashed'``     dashed line
-        ``'-.'`` or  ``'dash_dot'``   dash-dotted line
+        ``'-.'`` or  ``'dashdot'``    dash-dotted line
         ``':'`` or ``'dotted'``       dotted line
         ===========================   =================
 
diff --git a/lib/matplotlib/lines.py b/lib/matplotlib/lines.py
@@ -1011,7 +1011,7 @@ def set_linestyle(self, ls):
         ===========================   =================
         ``'-'`` or ``'solid'``        solid line
         ``'--'`` or  ``'dashed'``     dashed line
-        ``'-.'`` or  ``'dash_dot'``   dash-dotted line
+        ``'-.'`` or  ``'dashdot'``    dash-dotted line
         ``':'`` or ``'dotted'``       dotted line
         ``'None'``                    draw nothing
         ``' '``                       draw nothing
diff --git a/lib/matplotlib/patches.py b/lib/matplotlib/patches.py
@@ -370,7 +370,7 @@ def set_linestyle(self, ls):
         ===========================   =================
         ``'-'`` or ``'solid'``        solid line
         ``'--'`` or  ``'dashed'``     dashed line
-        ``'-.'`` or  ``'dash_dot'``   dash-dotted line
+        ``'-.'`` or  ``'dashdot'``    dash-dotted line
         ``':'`` or ``'dotted'``       dotted line
         ===========================   =================
 
