matplotlib-users Mailing List for matplotlib

On 2015-07-28 10:31,  (by way of c....@po...) wrote:
> I try to use a dates on the x-aches. With pure Python3 code it works
> fine. BUt when I try to use this inside wxPython application on a
> FigureCanvas it doesn't work. And I don't understand the difference
> here.
>
> This is the error
> [err]
>      plot.plot([datetime.date(2015, 1, 7),
> TypeError: descriptor 'date' requires a 'datetime.datetime' object but
> received a 'int'
> [/err]
>
> This is the fine working pure Python3 code.
<snip>
> import datetime
<snip>
> This is the piece of wxPython code that cause the error
<snip>
> from datetime import datetime

	There is the problem.  The error has nothing to do with matplotlib.  In 
one case you did "import datetime" and imported the datetime library. 
In the other you did "from datetime import datetime", thus importing the 
datetime type from that library.  If your first version is working, 
change the second version to use the same import.

-- 
Brendan Barnwell
"Do not follow where the path may lead.  Go, instead, where there is no 
path, and leave a trail."
    --author unknown

I try to use a dates on the x-aches. With pure Python3 code it works
fine. BUt when I try to use this inside wxPython application on a
FigureCanvas it doesn't work. And I don't understand the difference
here.

This is the error
[err]
    plot.plot([datetime.date(2015, 1, 7),
TypeError: descriptor 'date' requires a 'datetime.datetime' object but
received a 'int'
[/err]

This is the fine working pure Python3 code.
[code]
#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import matplotlib.pyplot as plt
import datetime

plt.plot([datetime.date(2015, 1, 7),
	  datetime.date(2015, 2, 5),
	  datetime.date(2015, 6, 2)],
	 [70.3, 60.1, 68.8])
plt.show()
[/code]

This is the piece of wxPython code that cause the error
[code]
# -*- coding: utf-8 -*-
import matplotlib.pyplot as pyplot
from matplotlib.backends.backend_wxagg import FigureCanvasWxAgg as
FigureCanvas
from datetime import datetime

#...

class StatisticTab(wx.Panel):
    def __init__(self, parent):
        super(StatisticTab, self).__init__(parent)

        panel = wx.Panel(self)

        fig = pyplot.figure()
        plot = self.fig.add_subplot(1,1,1)
        plot.plot([datetime.date(2015, 1, 7),
                   datetime.date(2015, 2, 5),
                   datetime.date(2015, 6, 2)],
                  [70.3, 60.1, 68.8])

        self.canvas = FigureCanvas(self, -1, fig)

        sizer = wx.BoxSizer(wx.VERTICAL)
        sizer.Add(panel)
        self.SetSizer(sizer)
[/code]

That makes sense. Thank you.

João

> On 28 Jul 2015, at 16:08, Oscar Benjamin <osc...@gm...> wrote:
> 
> 
> 
> On Tue, 28 Jul 2015 at 16:01 Joao Quinta da Fonseca <Joa...@ma...> wrote:
> 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. $\tau does not give an error but plots a strange character.
>  
> Can you help? thanks
> 
> This is to do with how Python handles strings and is not a matplotlib issue. The \ is an escape character in Python strings but only for certain letters e.g. \t is a tab character etc:
> 
> In [3]: print('$\tau$')
> $    au$
> 
> In [4]: print('$\alpha$')
> $lpha$
> 
> \g is not an escape so:
> 
> In [5]: print('$\gamma$')
> $\gamma$
> 
> To include slashes in your string you either need to double them up or use raw strings:
> 
> In [8]: print(r'$\alpha$')
> $\alpha$
> 
> In [9]: print('$\\alpha$')
> $\alpha$
> 
> --
> Oscar

On Tue, 28 Jul 2015 at 16:01 Joao Quinta da Fonseca <
Joa...@ma...> wrote:

> 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
>

This is to do with how Python handles strings and is not a matplotlib
issue. The \ is an escape character in Python strings but only for certain
letters e.g. \t is a tab character etc:

In [3]: print('$\tau$')
$    au$

In [4]: print('$\alpha$')
$lpha$

\g is not an escape so:

In [5]: print('$\gamma$')
$\gamma$

To include slashes in your string you either need to double them up or use
raw strings:

In [8]: print(r'$\alpha$')
$\alpha$

In [9]: print('$\\alpha$')
$\alpha$

--
Oscar

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)
>
>
>
>
> ------------------------------------------------------------------------------
> _______________________________________________
> Matplotlib-users mailing list
> Mat...@li...
> https://lists.sourceforge.net/lists/listinfo/matplotlib-users
>

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)