Mathtext markers in matplotlib

As I need to plot many curves in a single figure, I need many different types of markers. Sometimes the number of the default markers are not enough, so it would be nice if the user could customize the marker types.

According to the document page (http://matplotlib.sourceforge.net/api/artist_api.html#matplotlib.lines.Line2D.set_marker), it is possible to use mathtext as the marker. However, it did not work in my case.

plot(x, y, marker='$||$') # To use two vertical lines as the marker.

The error message is like this:

File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 3432, in plot
  for line in self._get_lines(*args, **kwargs):
File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 311, in _grab_next_args
  for seg in self._plot_args(remaining, kwargs):
File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 298, in _plot_args
  seg = func(x[:,j%ncx], y[:,j%ncy], kw, kwargs)
File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 248, in _makeline
  self.set_lineprops(seg, **kwargs)
File "/usr/lib/pymodules/python2.6/matplotlib/axes.py", line 191, in set_lineprops
  func(val)
File "/usr/lib/pymodules/python2.6/matplotlib/lines.py", line 804, in set_marker
  self._markerFunc = self._markers[marker]
KeyError: '$||$'

The matplotlib version is:

m开发者_如何学运维atplotlib.__version__
'0.99.1.1'

I also tried plot(x, y, marker=r'$||$'), which does not work either.

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Have you set text.usetex in your matplotrc file? You also need to use the right output backend, such as Postscript or PDF.