Re: [Matplotlib-users] Tex error in plot label

[Jens N. <jen...@gm...>]

I think you either need to escape the \ as \\ or use a raw string .i.e do
r'$\alpha$' otherwise \a gets interpreted as control character.

try entering '\alpha' in a regular python prompt and you will se what
happens.

Best
Jens

tir. 28. jul. 2015 kl. 16.01 skrev Joao Quinta da Fonseca <
Joa...@ma...>:

> I am trying to use LaTeX on the ylabel of a plot using:
>
> plt.ylabel("$\alpha$”)
>
> and I am seeing very inconsistent behaviour. If I use $\alpha$ I get an
> error (see below), but \gamma is fine. $\tau does not give an error but
> plots a strange character.
>
> Can you help? thanks
>
> Joao
>
>
> Using $\alpha$ like above gives a long error message:
>
> ---------------------------------------------------------------------------
> ValueError
>                                 Traceback (most recent call last)
>
> /Users/joao/anaconda/lib/python2.7/site-packages/IPython/core/formatters.pyc
> in __call__(self, obj)
>     328                 pass
>     329             else:
> --> 330                 return printer(obj)
>     331             # Finally look for special method names
>     332             method = _safe_get_formatter_method(obj,
> self.print_method)
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/IPython/core/pylabtools.pyc
> in <lambda>(fig)
>     205
>     206     if 'png' in formats:
> --> 207         png_formatter.for_type(Figure, lambda fig:
> print_figure(fig, 'png', **kwargs))
>     208     if 'retina' in formats or 'png2x' in formats:
>     209         png_formatter.for_type(Figure, lambda fig:
> retina_figure(fig, **kwargs))
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/IPython/core/pylabtools.pyc
> in print_figure(fig, fmt, bbox_inches, **kwargs)
>     115
>     116     bytes_io = BytesIO()
> --> 117     fig.canvas.print_figure(bytes_io, **kw)
>     118     data = bytes_io.getvalue()
>     119     if fmt == 'svg':
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/backend_bases.pyc
> in print_figure(self, filename, dpi, facecolor, edgecolor, orientation,
> format, **kwargs)
>    2156                     orientation=orientation,
>    2157                     dryrun=True,
> -> 2158
>                      **kwargs)
>
>    2159                 renderer = self.figure._cachedRenderer
>    2160                 bbox_inches = self.figure.get_tightbbox(renderer)
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc
> in print_png(self, filename_or_obj, *args, **kwargs)
>     519
>     520     def print_png(self, filename_or_obj, *args, **kwargs):
> --> 521         FigureCanvasAgg.draw(self)
>     522         renderer = self.get_renderer()
>     523         original_dpi = renderer.dpi
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc
> in draw(self)
>     467
>     468         try:
> --> 469             self.figure.draw(self.renderer)
>     470         finally:
>     471             RendererAgg.lock.release()
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/artist.pyc in
> draw_wrapper(artist, renderer, *args, **kwargs)
>      57     def draw_wrapper(artist, renderer, *args, **kwargs):
>      58         before(artist, renderer)
> ---> 59         draw(artist, renderer, *args, **kwargs)
>      60         after(artist, renderer)
>      61
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/figure.pyc in
> draw(self, renderer)
>    1083         dsu.sort(key=itemgetter(0))
>    1084         for zorder, a, func, args in dsu:
> -> 1085             func(*args)
>    1086
>    1087         renderer.close_group('figure')
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/artist.pyc in
> draw_wrapper(artist, renderer, *args, **kwargs)
>      57     def draw_wrapper(artist, renderer, *args, **kwargs):
>      58         before(artist, renderer)
> ---> 59         draw(artist, renderer, *args, **kwargs)
>      60         after(artist, renderer)
>      61
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/axes/_base.pyc
> in draw(self, renderer, inframe)
>    2108
>    2109         for zorder, a in dsu:
> -> 2110             a.draw(renderer)
>    2111
>    2112         renderer.close_group('axes')
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/artist.pyc in
> draw_wrapper(artist, renderer, *args, **kwargs)
>      57     def draw_wrapper(artist, renderer, *args, **kwargs):
>      58         before(artist, renderer)
> ---> 59         draw(artist, renderer, *args, **kwargs)
>      60         after(artist, renderer)
>      61
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/axis.pyc in
> draw(self, renderer, *args, **kwargs)
>    1126         self._update_label_position(ticklabelBoxes,
> ticklabelBoxes2)
>    1127
> -> 1128         self.label.draw(renderer)
>    1129
>    1130         self._update_offset_text_position(ticklabelBoxes,
> ticklabelBoxes2)
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/artist.pyc in
> draw_wrapper(artist, renderer, *args, **kwargs)
>      57     def draw_wrapper(artist, renderer, *args, **kwargs):
>      58         before(artist, renderer)
> ---> 59         draw(artist, renderer, *args, **kwargs)
>      60         after(artist, renderer)
>      61
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/text.pyc in
> draw(self, renderer)
>     593         renderer.open_group('text', self.get_gid())
>     594
> --> 595         bbox, info, descent = self._get_layout(renderer)
>     596         trans = self.get_transform()
>     597
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/text.pyc in
> _get_layout(self, renderer)
>     318
>                  w, h, d =
> renderer.get_text_width_height_descent(clean_line,
>
>     319
>  self._fontproperties,
> --> 320
>                                                          ismath=ismath)
>
>     321             else:
>     322                 w, h, d = 0, 0, 0
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/backends/backend_agg.pyc
> in get_text_width_height_descent(self, s, prop, ismath)
>     226         if ismath:
>     227             ox, oy, width, height, descent, fonts, used_characters
> = \
> --> 228                 self.mathtext_parser.parse(s, self.dpi, prop)
>     229             return width, height, descent
>     230
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/mathtext.pyc
> in parse(self, s, dpi, prop)
>    3003             self.__class__._parser = Parser()
>    3004
> -> 3005         box = self._parser.parse(s, font_output, fontsize, dpi)
>    3006         font_output.set_canvas_size(box.width, box.height,
> box.depth)
>    3007         result = font_output.get_results(box)
>
>
>
> /Users/joao/anaconda/lib/python2.7/site-packages/matplotlib/mathtext.pyc
> in parse(self, s, fonts_object, fontsize, dpi)
>    2337                         err.line,
>    2338                         " " * (err.column - 1) + "^",
> -> 2339
>                          six.text_type(err)]))
>
>    2340         self._state_stack = None
>    2341         self._em_width_cache = {}
>
>
>
> ValueError
> :
> $ lpha$
> ^
> Expected end of text (at char 0), (line:1, col:1)
>
>
>
>
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