matplotlib-users Mailing List for matplotlib

On 2015年07月28日 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 2015年7月28日 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 2015年7月28日 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)