added markevery property to Line2D

svn path=/trunk/matplotlib/; revision=6631

Author: jdh2358

CHANGELOG

@@ -1,3 +1,6 @@
+2008-12-16 Added markevery property to Line2D to support subsampling
+           of markers - JDH
+
 2008-12-15 Removed mpl_data symlink in docs.  On platforms that do not
            support symlinks, these become copies, and the font files
            are large, so the distro becomes unneccessarily bloaded.

doc/users/pyplot_tutorial.rst

@@ -117,6 +117,7 @@ markeredgecolor or mec	any matplotlib color
 markeredgewidth or mew	float value in points
 markerfacecolor or mfc	any matplotlib color
 markersize or ms	float
+markevery               None | integer | (startind, stride)
 picker			used in interactive line selection
 pickradius		the line pick selection radius
 solid_capstyle		['butt' | 'round' |  'projecting']

lib/matplotlib/lines.py

@@ -177,6 +177,7 @@ def __init__(self, xdata, ydata,
                  solid_joinstyle = None,
                  pickradius      = 5,
                  drawstyle       = None,
+                 markevery       = None,
                  **kwargs
                  ):
         """
@@ -226,6 +227,7 @@ def __init__(self, xdata, ydata,
         self.set_linewidth(linewidth)
         self.set_color(color)
         self.set_marker(marker)
+        self.set_markevery(markevery)
         self.set_antialiased(antialiased)
         self.set_markersize(markersize)
         self._dashSeq = None
@@ -320,6 +322,32 @@ def setpickradius(self,d):
         """
         self.pickradius = d
 
+
+    def set_markevery(self, every):
+        """
+        Set the markevery property to subsample the plot when using
+        markers.  Eg if ``markevery=5``, every 5-th marker will be
+        plotted.  *every* can be
+
+        None
+            Every point will be plotted
+
+        an integer N
+            Every N-th marker will be plotted starting with marker 0
+
+        A length-2 tuple of integers
+            every=(start, N) will start at point start and plot every N-th marker
+
+
+        ACCEPTS: None | integer | (startind, stride)
+
+        """
+        self._markevery = every
+
+    def get_markevery(self):
+        'return the markevery setting'
+        return self._markevery
+
     def set_picker(self,p):
         """Sets the event picker details for the line.
 
@@ -472,6 +500,19 @@ def draw(self, renderer):
             funcname = self._markers.get(self._marker, '_draw_nothing')
             if funcname != '_draw_nothing':
                 tpath, affine = self._transformed_path.get_transformed_points_and_affine()
+
+                # subsample the markers if markevery is not None
+                markevery = self.get_markevery()
+                if markevery is not None:
+                    if iterable(markevery):
+                        startind, stride = markevery
+                    else:
+                        startind, stride = 0, markevery
+                        if tpath.codes is not None:
+                            tpath.codes = tpath.codes[startind::stride]
+                        tpath.vertices = tpath.vertices[startind::stride]
+
+
                 markerFunc = getattr(self, funcname)
                 markerFunc(renderer, gc, tpath, affine.frozen())
 

unit/nose_tests.py

@@ -1,17 +1,43 @@
+import numpy as np
+
 import nose, nose.tools as nt
 import numpy.testing as nptest
 
 import matplotlib
 matplotlib.use('Agg')
-import numpy as np
 import matplotlib.pyplot as plt
 import matplotlib.axes as maxes
 
 def test_create_subplot_object():
     fig = plt.figure()
     ax = maxes.Subplot(fig, 1, 1, 1)
     fig.add_subplot(ax)
+    plt.close(fig)
+
+def test_markevery():
+    x, y = np.random.rand(2, 100)
+
+    # check marker only plot
+    fig = plt.figure()
+    ax = fig.add_subplot(111)
+    ax.plot(x, y, 'o')
+    ax.plot(x, y, 'd', markevery=None)
+    ax.plot(x, y, 's', markevery=10)
+    ax.plot(x, y, '+', markevery=(5, 20))
+    fig.canvas.draw()
+    plt.close(fig)
+
+    # check line/marker combos
+    fig = plt.figure()
+    ax = fig.add_subplot(111)
+    ax.plot(x, y, '-o')
+    ax.plot(x, y, '-d', markevery=None)
+    ax.plot(x, y, '-s', markevery=10)
+    ax.plot(x, y, '-+', markevery=(5, 20))
+    fig.canvas.draw()
+    plt.close(fig)
 
 if __name__=='__main__':
     nose.runmodule(argv=['-s','--with-doctest'], exit=False)
-    pass
+
+    plt.show()