fix the filtering of non-integer ticks in maxNlocator with integer = True #12087

dabana · 2018-09-11T01:25:19Z

Reference to issue #12072

PR Summary

Handling of the integer keyword does not seem right

   *integer*
     If True, ticks will take only integer values, provided
     at least `min_n_ticks` integers are found within the
     view limits.

When True it is supposed to provide only integer values for tick label. Here is the outputs printed out at different steps in the code. We first start by the list of possible tick spacing, self.extended_steps:

self._extended_steps = [ 0.1   0.15  0.2   0.25  0.3   0.4   0.5   0.6   0.8   1.    1.5   2.
  2.5   3.    4.    5.    6.    8.   10.   15.  ]

Then we multiply it by scale:

scale = 1000000000.0
steps = self._extended_steps * scale
steps = [1.0e+08 1.5e+08 2.0e+08 2.5e+08 3.0e+08 4.0e+08 5.0e+08 6.0e+08 8.0e+08 1.0e+09 1.5e+09 2.0e+09 2.5e+09 3.0e+09 4.0e+09 5.0e+09 6.0e+09 8.0e+09
 1.0e+10 1.5e+10]

Then comes the two lines of code that are supposed to filter the ticks < 1 and keep only integer ticks.

        if self._integer:
            # For steps > 1, keep only integer values.
            igood = (steps < 1) | (np.abs(steps - np.round(steps)) < 0.001)
            steps = steps[igood]

The result of this filtering is:

steps = [1.0e+08 1.5e+08 2.0e+08 2.5e+08 3.0e+08 4.0e+08 5.0e+08 6.0e+08 8.0e+08
 1.0e+09 1.5e+09 2.0e+09 2.5e+09 3.0e+09 4.0e+09 5.0e+09 6.0e+09 8.0e+09
 1.0e+10 1.5e+10]

This does not seem correct. The following PR suggest changes to the code that produces the following output:

self._extended_steps = [ 0.1   0.15  0.2   0.25  0.3   0.4   0.5   0.6   0.8   1.    1.5   2.
  2.5   3.    4.    5.    6.    8.   10.   15.  ]

FIRST, filtering of non-integer ticks:

steps = [ 1.  2.  3.  4.  5.  6.  8. 10. 15.]

THEN, multiplication by scale

scale = 1000000000.0
steps = self._extended_steps * scale 
steps = [1.0e+09 2.0e+09 3.0e+09 4.0e+09 5.0e+09 6.0e+09 8.0e+09 1.0e+10 1.5e+10]

PR Checklist

Has Pytest style unit tests
Code is Flake 8 compliant
New features are documented, with examples if plot related
Documentation is sphinx and numpydoc compliant
Added an entry to doc/users/next_whats_new/ if major new feature (follow instructions in README.rst there)
Documented in doc/api/api_changes.rst if API changed in a backward-incompatible way

… True*. Reference issue matplotlib#12072

efiring · 2018-09-11T03:40:09Z

I don't understand the point of this PR; I think the existing code is doing what it is intended to do, as described by the docstring. Can you supply a minimal example of a plot where using "integer=True" does something other than what the docstring says?

dabana · 2018-09-11T12:50:13Z

import matplotlib.pyplot as plt
import matplotlib.ticker as ticker

sci_nums = [10**9, 8*10**9]
fig, (axl, axr) = plt.subplots(1,2)
      
axl.scatter(range(len(sci_nums)), sci_nums)
axl.yaxis.set_major_locator(ticker.MaxNLocator(4, integer = True))
axl.set_title('with integer = True\n')

axr.scatter(range(len(sci_nums)), sci_nums)
axr.yaxis.set_major_locator(ticker.MaxNLocator(4, integer = False))
axr.set_title('with integer = False\n')

Output is:

dabana · 2018-09-11T12:58:42Z

I guess I am confused with what the integer keyword is supposed to do. I thought all the tick labels would end-up greater than 1 without decimals (like 1, 2, 3 ... or 3, 6, 9, etc...).

By reading the code, I understand than only the tick labels greater than 1 will be integer.

        if self._integer:
            # For steps > 1, keep only integer values.
            igood = (steps < 1) | (np.abs(steps - np.round(steps)) < 0.001)
            steps = steps[igood]

If this is the correct behavior it might be worth rewording the doc_string to make this clear. For exemple:

integer
If True, ticks greater than 1 will take only integer values, provided
at least min_n_ticks integers are found within the
view limits.

dabana · 2018-09-11T13:23:55Z

I am closing this PR and moving the conversation to issue #12072

dabana added 2 commits September 10, 2018 21:09

fix the filtering of non-integer ticks in maxNlocator with *integer =…

18dcc86

… True*. Reference issue matplotlib#12072

remove all debug features

91f570b

QuLogic requested a review from efiring September 11, 2018 01:33

dabana closed this Sep 11, 2018

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fix the filtering of non-integer ticks in maxNlocator with integer = True #12087

fix the filtering of non-integer ticks in maxNlocator with integer = True #12087

dabana commented Sep 11, 2018 •

edited

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efiring commented Sep 11, 2018

dabana commented Sep 11, 2018

dabana commented Sep 11, 2018

dabana commented Sep 11, 2018

fix the filtering of non-integer ticks in maxNlocator with *integer = True* #12087

fix the filtering of non-integer ticks in maxNlocator with *integer = True* #12087

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dabana commented Sep 11, 2018 • edited Loading

PR Summary

PR Checklist

efiring commented Sep 11, 2018

dabana commented Sep 11, 2018

dabana commented Sep 11, 2018

dabana commented Sep 11, 2018

fix the filtering of non-integer ticks in maxNlocator with integer = True #12087

fix the filtering of non-integer ticks in maxNlocator with integer = True #12087

dabana commented Sep 11, 2018 •

edited

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