title: Plot with fewer markers than data points (or a better way to plot CDFs?) [matplotlib, or general plotting help]
body: <p>I am plotting Cumulative Distribution Functions, with a large number of data points. I am plotting a few lines on the same plot, which are identified with markers as it will be printed in black and white. What I would like are markers evenly spaced in the x-dimension. What I am getting is one marker per data point (and given the number of points, they all overlap)</p>
  
  <p>I'm not sure if it's my understanding of how to plot well, or just a lack of understanding matplotlib. I can't find a 'marker frequency' setting. </p>
  
  <p>An easy solution for one line would be to take every N'th value from the line, and use that as a separate line with linestyle='', but I would like the markers to be vertically aligned, and the different x arrays have different lengths. </p>
  
  <pre><code># in reality, many thousands of values
  x_example = [ 567, 460, 66, 1034, 275, 26, 628, 99, 287, 157, 705, 421, 1093, \ 
       139, 204, 14, 240, 179, 94, 139, 645, 670, 47, 520, 891, 450, 56, 964,   \
       1728, 99, 277, 356, 1628, 745, 364, 88, 112, 810, 816, 523, 401, 89,     \ 
       278, 917, 370, 53, 39, 90, 853, 356 ] 
  x = sort(x_example)
  y = linspace(0,1,len(x))
  
  ax = subplot(1,1,1)
  plots[w] = ax.plot(x,y, marker='o')
  </code></pre>