[Bug]: unintended space between comma and digit when using useMathText = True together with comma as decimal separator #23626

der-zi · 2022-08-15T17:38:48Z

Bug summary

When I turn on "useMathText" in matplotlib in the intention to replace 1e6 by $\times 10^6$, the formatting of the commas in the tick labels themselves get wrong. Before they are correct in the form "3,5", with "useMathText" they become "3, 5", with (half?) a whitespace between the comma and the following digit.

Code for reproduction

%matplotlib inline
import locale
locale.setlocale(locale.LC_ALL, "deu_deu")
import matplotlib.pyplot as plt

plt.rcParams['axes.formatter.use_locale'] = True

fig, ax = plt.subplots()
x = [1000, 2000, 3000, 3.5e6]
y = [1, 4, 3, 5]
ax.plot(x, y, linestyle = "", marker = "o")
ax.set_xlabel("the x-axis")
ax.ticklabel_format(axis = 'x', useMathText = True)

Actual outcome

the formatting of the decimal power is altered, but the ticklabels themselves are rendered incorrectly (additional space between comma and following digit)

Expected outcome

the formatting of the decimal power is altered, and the ticklabels themselves are rendered correctly (as before adding useMathText = True)

Additional information

apparently, matplotlib uses LaTeX to render the mathematical notation of power, and also changes the way the normal ticklabels are created to TeX mode.
however, when using comma as decimal separator in TeX you have to consider that it is written by americans, using the comma as an element separator, not decimal separator, and therefore in standard configuration automatically adds a space behind the comma.

this can be fixed by using
3{,}5
or
3,\!5
or
\num{3,5} or \num{3.5} with siunitx configured correctly
or with the package icomma.

(Also, when already using the locale set to german, one could be expecting \cdot rather than \times. There should be an option to choose between these)

Operating system

No response

Matplotlib Version

3.5.3

Matplotlib Backend

module://matplotlib_inline.backend_inline

Python version

3.9.7

Jupyter version

6.4.10

Installation

pip

oscargus · 2022-08-15T18:00:45Z

This is probably the place to fix it:

matplotlib/lib/matplotlib/ticker.py

Lines 531 to 536 in d3038bf

    
               def _format_maybe_minus_and_locale(self, fmt, arg): 
        
                   """ 
        
                   Format *arg* with *fmt*, applying Unicode minus and locale if desired. 
        
                   """ 
        
                   return self.fix_minus(locale.format_string(fmt, (arg,), True) 
        
                                         if self._useLocale else fmt % arg)

The main issue is most likely how to deal with format strings that already includes a ,... Probably one should try and escape those somehow, replace ',' with '{,}' and get rid of the escapes. Given that self._useMathText is True.

oscargus · 2022-08-15T18:17:40Z

For \cdot vs \times, probably the most feasible way is to provide configuration using something like rcParams['text.formatter.exponent_separator'] (or whatever a better name is).

anntzer · 2022-08-31T09:05:44Z

The main issue is most likely how to deal with format strings that already includes a ,

A possibility is perhaps to just copypaste the logic of python's format_string (https://github.com/python/cpython/blob/f7e7bf161aaec5a5cffdcec7c97e1f09e445421b/Lib/locale.py#L213), split out format specifiers and non-specifiers and brace-escape the non-specifiers.

oscargus · 2022-09-12T08:33:35Z

Marking as a good first issue, but medium, as it is well defined what should happen, but maybe not so straightforward to solve.

evanandresen · 2022-09-25T21:47:37Z

Currently working on this issue.

evanandresen · 2022-09-28T18:29:15Z

This is probably the place to fix it:

matplotlib/lib/matplotlib/ticker.py

Lines 531 to 536 in d3038bf

def _format_maybe_minus_and_locale(self, fmt, arg):

"""

Format *arg* with *fmt*, applying Unicode minus and locale if desired.

"""

return self.fix_minus(locale.format_string(fmt, (arg,), True)

if self._useLocale else fmt % arg)

The main issue is most likely how to deal with format strings that already includes a ,... Probably one should try and escape those somehow, replace ',' with '{,}' and get rid of the escapes. Given that self._useMathText is True.

I have a quick fix PR ready to submit that changes the "," to "{,}" under the given conditions. I'm unsure how I would implement a pytest for this change. Is it necessary because it is a small and mostly visual change and if so does anyone have advice on what to assert?

evanandresen · 2022-09-28T18:49:34Z

It looks like my fix actually messes up the xy values of the cursor location. What exactly is this feature of the plot called so I can find it in the code? (The plot element that shows the coordinates of the cursor)

oscargus · 2022-09-29T06:46:49Z

It is set with set_message and the formatting is done using _mouse_event_to_message.

matplotlib/lib/matplotlib/backend_bases.py

Lines 3044 to 3072 in a283d20

    
           @staticmethod 
        
           def _mouse_event_to_message(event): 
        
               if event.inaxes and event.inaxes.get_navigate(): 
        
                   try: 
        
                       s = event.inaxes.format_coord(event.xdata, event.ydata) 
        
                   except (ValueError, OverflowError): 
        
                       pass 
        
                   else: 
        
                       s = s.rstrip() 
        
                       artists = [a for a in event.inaxes._mouseover_set 
        
                                  if a.contains(event)[0] and a.get_visible()] 
        
                       if artists: 
        
                           a = cbook._topmost_artist(artists) 
        
                           if a is not event.inaxes.patch: 
        
                               data = a.get_cursor_data(event) 
        
                               if data is not None: 
        
                                   data_str = a.format_cursor_data(data).rstrip() 
        
                                   if data_str: 
        
                                       s = s + '\n' + data_str 
        
                       return s 
        
           def mouse_move(self, event): 
        
               self._update_cursor(event) 
        
               s = self._mouse_event_to_message(event) 
        
               if s is not None: 
        
                   self.set_message(s) 
        
               else: 
        
                   self.set_message(self.mode)

oscargus · 2022-09-29T06:57:20Z

For the testing, it probably makes sense to have a parameterized test for a few locales (one using , and one using .).
https://docs.python.org/3/library/locale.html
Set up the locale, set up an Axes with relevant limits and check the tick labels.

@pytest.mark.parametrize("loc, result", (('DE', (r'3,5 \times 10^3', ...))
def test_locale_comma(loc, result):
   locale.setlocale(locale.LC_ALL, loc)
  ...
  assert ... == result

Maybe even create a formatter that uses a , elsewhere and use that to check that it becomes correct (although it is, sort of, a quite unusual case).

devRD · 2023-02-11T07:18:56Z

Is anyone working on this issue? I would like to work on this issue following the discussion here and the discussion from #24079

rcomer · 2023-02-11T09:43:23Z

Thanks @devRD, it seems likely that #24079 has stalled, so I think it’s fine to pick this up if you are interested. It would be good to bring it to a conclusion.

oscargus added the topic: text/mathtext label Aug 15, 2022

oscargus added Difficulty: Medium https://matplotlib.org/devdocs/devel/contribute.html#good-first-issues Good first issue Open a pull request against these issues if there are no active ones! labels Sep 12, 2022

oscargus mentioned this issue Oct 3, 2022

Escape space after comma as decimal seperator #24079

Closed

2 tasks

devRD mentioned this issue Feb 16, 2023

Fix unintended space after comma as a decimal separator #25226

Merged

6 tasks

ksunden closed this as completed in #25226 Mar 28, 2023

QuLogic added this to the v3.8.0 milestone Mar 28, 2023

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[Bug]: unintended space between comma and digit when using useMathText = True together with comma as decimal separator #23626

[Bug]: unintended space between comma and digit when using useMathText = True together with comma as decimal separator #23626

der-zi commented Aug 15, 2022 •

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oscargus commented Aug 15, 2022 •

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oscargus commented Aug 15, 2022

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anntzer commented Aug 31, 2022

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oscargus commented Sep 12, 2022

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evanandresen commented Sep 25, 2022

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evanandresen commented Sep 28, 2022

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evanandresen commented Sep 28, 2022

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oscargus commented Sep 29, 2022

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oscargus commented Sep 29, 2022

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devRD commented Feb 11, 2023

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rcomer commented Feb 11, 2023

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[Bug]: unintended space between comma and digit when using useMathText = True together with comma as decimal separator #23626

[Bug]: unintended space between comma and digit when using useMathText = True together with comma as decimal separator #23626

Comments

der-zi commented Aug 15, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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Bug summary

Code for reproduction

Actual outcome

Expected outcome

Additional information

Operating system

Matplotlib Version

Matplotlib Backend

Python version

Jupyter version

Installation

oscargus commented Aug 15, 2022 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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oscargus commented Aug 15, 2022

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anntzer commented Aug 31, 2022

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oscargus commented Sep 12, 2022

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evanandresen commented Sep 25, 2022

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evanandresen commented Sep 28, 2022

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evanandresen commented Sep 28, 2022

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oscargus commented Sep 29, 2022

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oscargus commented Sep 29, 2022

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devRD commented Feb 11, 2023

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rcomer commented Feb 11, 2023

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der-zi commented Aug 15, 2022 •

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oscargus commented Aug 15, 2022 •

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