8000 DOC: Better error when float on datetime axis by jklymak · Pull Request #10084 · matplotlib/matplotlib · GitHub
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DOC: Better error when float on datetime axis #10084

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Merged
merged 1 commit into from
Dec 28, 2017
Merged

DOC: Better error when float on datetime axis #10084

merged 1 commit into from
Dec 28, 2017

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jklymak
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@jklymak jklymak commented Dec 24, 2017

PR Summary

#9211 points out that the error message after

import matplotlib.pyplot as plt
from datetime import datetime

fig, ax = plt.subplots()
ax.plot(datetime(2017, 1, 1), 1)
ax.plot(1, 1)
plt.show()

yields the mysterious error:

ValueError: ordinal must be >= 1

This PR catches earlier and returns:

ValueError: view limit minimum -36815.450000000004 < 1. This often happens if you pass a float to an axis that has datetime units

PR Checklist

  • Has Pytest style unit tests
  • Code is PEP 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

anntzer
anntzer reviewed Dec 24, 2017
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lib/matplotlib/dates.py Outdated

if dmin < 1:
raise ValueError('datalim minimum {} < 1. This often '
'happens if you pass a float to an '
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indent

anntzer
anntzer reviewed Dec 24, 2017
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lib/matplotlib/dates.py Outdated
raise ValueError('cannot convert {} < 1 to a date. This '
'often happens if floats are passed to '
'a Matplotlib axis that expects datetime objects. '
''.format(ix))
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you don't need the '', starting the line with a dot binds to the string on the previous line

anntzer
anntzer reviewed Dec 24, 2017
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lib/matplotlib/dates.py Outdated
if ix < 1:
raise ValueError('cannot convert {} < 1 to a date. This '
'often happens if floats are passed to '
'a Matplotlib axis that expects datetime objects. '
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to an axis (no need to mpl, which you also did not include below)

anntzer
anntzer approved these changes Dec 24, 2017
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minor formatting/wording can be improved but nothing blocking

@jklymak jklymak force-pushed the doc-better-data-error branch from f02880f to 50969c4 Compare December 24, 2017 19:49
dstansby
dstansby reviewed Dec 24, 2017
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lib/matplotlib/dates.py Outdated

if dmin < 1:
raise ValueError('datalim minimum {} < 1. This often '
'happens if you pass a float to an '
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Can "float" be change to something less technical like "number" or "normal number"?

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@story645 story645 Dec 25, 2017 •
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value that is not a datetime?

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(apart from my suggested change I am +10000 on this, since I remember in my early Matplotlib days spending ages meaning what on earth the current error message meant)

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jklymak commented Dec 26, 2017

Yep I’ll fix it this pm. No problem making it even clearer.

@jklymak jklymak force-pushed the doc-better-data-error branch from 50969c4 to 88a19c2 Compare December 26, 2017 22:55
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jklymak commented Dec 26, 2017

Done - I couldn't get a test to work, however. 🐑 If I do:

g, ax = plt.subplots()
ax.plot(datetime(2017, 1, 1), 1)
ax.plot(1, 1)
fig.draw(fig.canvas.get_renderer())

I get the error. Trying to do this in dates_test.py I get:

  def test_bad_datetime():
        with pytest.raises(ValueError):
            fig, ax = plt.subplots()
            ax.plot(datetime.datetime(2017, 1, 1), 1)
            ax.plot(1, 1)
>           fig.draw(fig.canvas.get_renderer())
E           Failed: DID NOT RAISE <class 'ValueError'>

phobson
phobson reviewed Dec 26, 2017
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lib/matplotlib/dates.py Outdated
@@ -282,6 +283,11 @@ def _from_ordinalf(x, tz=None):
tz = _get_rc_timezone()

ix = int(x)
if ix < 1:
raise ValueError('cannot convert {} < 1 to a date. This '
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I think should be:
cannot convert {} to a date

{} < 1 evaluate to a bool 😉

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OK. Changed to

                             'view limit minimum {} is less than 1 and '
                             'is an invalid Matplotlib date value. This '
                             'often happens if you pass a non-datetime '
                             'value to an axis that has datetime units'
                             .format(vmin))

@jklymak jklymak force-pushed the doc-better-data-error branch from 88a19c2 to 38b137b Compare December 26, 2017 23:49
@jklymak jklymak force-pushed the doc-better-data-error branch from 38b137b to a4759e8 Compare December 27, 2017 05:12
@dstansby dstansby added this to the v2.2 milestone Dec 28, 2017
@dstansby dstansby merged commit dfc3a79 into matplotlib:master Dec 28, 2017
pauldmccarthy added a commit to pauldmccarthy/fsleyes that referenced this pull request Jan 3, 2018
@pauldmccarthy
Workaround matplotlib bug - always saving as png when format not spec…
b8e9521 
…ified:

matplotlib/matplotlib#10084
@QuLogic QuLogic modified the milestones: needs sorting, v2.2.0 Feb 12, 2018
This was referenced Mar 24, 2018
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@jklymak jklymak deleted the doc-better-data-error branch April 8, 2018 19:16
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@anntzer anntzer anntzer approved these changes

@dstansby dstansby dstansby approved these changes

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