This PR changes colorbar to draw fromself.vmin toself.vmax instead of from 0 to 1 so thatAutoTickLocator can work. Only modifies ticks if no boundaries are specified (i.e. contours).

See#9246

example:

importmatplotlib.pyplotaspltimportmatplotlib.colorsasmcolorsimportnumpyasnpX=np.random.randn(32,32)fig,ax=plt.subplots(2,2,figsize=(5,5),tight_layout=True)fornn,shrinkinenumerate([1.,0.4]):formm,loginenumerate([False,True]):iflog:norm=mcolors.LogNorm()Y=10**Xelse:norm=NoneY=Xpc=ax[nn,mm].pcolormesh(Y,norm=norm)ax[nn,mm].set_xticks([])ax[nn,mm].set_yticks([])fig.colorbar(pc,ax=ax[nn,mm],shrink=shrink,extend='both')plt.show()fig.savefig('ExampleCBOld.png')

before:

after:

PR Checklist

Test/get to work LogNorm
Has Pytest style unit tests
Code is PEP 8 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

tacaswell added this to thev2.2 milestone

Dec 1, 2017

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jklymak commentedDec 1, 2017

OK, this failed enough tests that there are a bunch more edge cases I need to consider. Good thing there are tests. I'll probably re-do this from scratch and try to make it less invasive. Ido think this is reasonable for 2.2, though, because I'll keep plugging away at it.

jklymak force-pushed theenh-colorbar-ticks branch 2 times, most recently from9d1146d to5c48c10Compare

December 2, 2017 06:48

jklymak changed the title~~WIP: ENH: adjustable colorbar ticks~~ENH: adjustable colorbar ticks

Dec 2, 2017

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jklymak commentedDec 2, 2017

This is redone, and much simpler now. 4 image files had to be changed...

jklymak force-pushed theenh-colorbar-ticks branch from5c48c10 to1d4160cCompare

December 2, 2017 21:58

jklymak force-pushed theenh-colorbar-ticks branch from338c0a1 toa31caddCompare

December 19, 2017 20:55

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jklymak commentedDec 19, 2017

Ping@efiringLogNorm() now works. I'm too lazy to doSymLogNorm() (well actually I disapprove of that normalization as a valid thing to do to data), but someone could easily figure it out.

The diff looks worse than it is because I moved a bit of code around.

jklymak commented

Dec 19, 2017

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lib/matplotlib/colorbar.py Outdated


		self._set_label()

		def _get_ticker_locator_formatter(self):

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jklymakDec 19, 2017

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Much of this was jut factored out of_ticker() But note the new locators for LogNorm and the fallback...

jklymak mentioned this pull request

Dec 20, 2017

Blank colorbars for high dynamic range LogNorm imshow plots#10051

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dstansby previously requested changes

Dec 24, 2017

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Some questions/comments, looks like this is good overall though

lib/matplotlib/colorbar.py Outdated

		This locator is just a `.MaxNLocator` except the min and max are
		clipped by the norm's min and max (i.e. vmin/vmax from the
		image/pcolor/contour object). This is necessary so ticks don't
		extrude into the "extend regions".

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dstansbyDec 24, 2017

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Shouldn't the docstring line up with the left of the quote marks?

lib/matplotlib/colorbar.py Outdated

		extrude into the "extend regions".
		"""

		def __init__(self, colorbar, args, *kwargs):

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dstansbyDec 24, 2017

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Why are there args and kwargs here if they're not used? Can this also get a docstring (just for the colorbar parameter is probably fine)

lib/matplotlib/colorbar.py

		extrude into the "extend regions".

		"""
		def __init__(self, colorbar, args, *kwargs):

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dstansbyDec 24, 2017

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Same as above comment on__init__

lib/matplotlib/colorbar.py Outdated

		X, Y = self._mesh()
		C = self._values[:, np.newaxis]
		self._config_axes(X, Y)
		if self.filled:
		self._add_solids(X, Y, C)
		# self._set_view_limits()

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Is this old debug code that needs to be removed?

lib/matplotlib/colorbar.py Outdated

		if (isinstance(self.norm, colors.LogNorm)
		and self._use_adjustable()):
		ax.set_xscale('log')
		ax.set_yscale('log')

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dstansbyDec 24, 2017

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and only the yscale be log here?

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jklymakDec 24, 2017

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They both need to be log to make theaspect kwarg work properly (... or we could do a bunch of math and make the X values make the aspect ratio right.)

lib/matplotlib/colorbar.py Outdated


		self._set_label()

		def _get_ticker_locator_formatter(self):

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This method could do with a quick comment underneath to explain what it does.

lib/matplotlib/colorbar.py Outdated

		else:
		b = self._boundaries[self._inside]
		locator = ticker.FixedLocator(b, nbins=10)
		# locator, formatter = _get_ticker_locator_formatter()

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This commented out line can go

jklymak force-pushed theenh-colorbar-ticks branch from452e401 to5972691Compare

December 24, 2017 18:00

dstansby self-assigned this

Dec 24, 2017

jklymak requested review fromefiring and removed request forefiring

January 10, 2018 03:38

jklymak modified the milestones:v2.2,v3.0

Jan 10, 2018

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jklymak commentedJan 10, 2018

Pushed to 3.0 as this isn't urgent. But I think it'd be easy to put in 2.2 if someone wants to dive in and re-milestone...

jklymak mentioned this pull request

Feb 4, 2018

[ENH] Unit support for ScalarMappables#7383

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jklymak force-pushed theenh-colorbar-ticks branch from5972691 to402b4d3Compare

February 4, 2018 18:15

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jklymak commentedFeb 4, 2018

rebased

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jklymak commentedFeb 4, 2018

@dstansby I think I addressed all your concerns.
@efiring requesting a review from you (though no rush) as this is your bailiwick...

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February 4, 2018 18:18

dstansby dismissed theirstale review

February 4, 2018 19:12

Old review

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efiring commentedFeb 5, 2018

The before-and-after comparison looks great, but tests seem to be failing now.

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jklymak commentedFeb 5, 2018

Yeah, its just the streamplot image test at 0.036 tolerance. I'll try to track it down. It passes on my machine and I took the text out so it can't be freetype. Grrrr.

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Feb 19, 2018

FIX: No rcparam minor ticks in colorbar #8358#10530

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skotaro commentedFeb 20, 2018•
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I'm not sure that this is the right place to tell this, but I recently wrote a detailed instruction on colorbar in matplotlib which might contribute for improving tutorials about colorbar.
https://qiita.com/skotaro/items/01d66a8c9902a766a2c0
It's only in Japanese for the moment but I think you can get the ideas from figures and sample codes. Main topics are 1. Anatomy of a colorbar, 2. Putting a colorbar at the right place with the right size, and 3. Changing ticker into log scale nicely. It's not comprehensive but I think it still helps users puzzled by colorbar.

After writing it, fortunately or not, I found this PR which seems to change colorbar's behavior significantly (no pseudo minor ticks, no normalization of vmin/vmax to 0/1, for example). Actually these modified behaviors are parts of the main topics in my instruction. Then I'm wondering whether I should translate the introduction as it is into English and make a PR to improve docs for the current behavior of colorbar (about cbar.ticker, especially), or I should wait for this PR to be implemented in, say, next rc version and revise the instruction to catch up the new behaviors. What do you think?

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jklymak commentedFeb 20, 2018

@skotaro Sounds like we had some similar difficulties with colorbars. I will push in the near future for this PR to get in, but it won’t be part of the distribution until 3.0 (July/Aug).

You may want to checkout constrained layout in 2.2Rc1 for easier colorbar placement. That doesn’t preclude a tutorial that explains how to fix things manually, but I’d suggest such a tutorial should at least reference the automated methods.

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efiring commentedMar 18, 2018

The problem with the doc build is that after the merge, the sphinx conf.pyexclude_patterns list is out of sync with the location where you are putting your users/whats_new file.
It looks like this is a bug in master: there are directories users/prev_whats_new and users/next_whats_new, butexclude_patterns = ['api/api_changes/*', 'users/whats_new/*'].

jklymak force-pushed theenh-colorbar-ticks branch 5 times, most recently from651d609 to2c33640Compare

March 18, 2018 04:58

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jklymak commentedMar 18, 2018

Somehow the doc build didn't like the name I had for the whats-new file. Works fine now. 🤷‍♂️

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Mar 18, 2018

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lib/matplotlib/colorbar.py Outdated

		ax.xaxis.get_major_formatter().set_offset_string(offset_string)
		_log.debug('Using fixed locator on colorbar')
		ticks, ticklabels, offset_string = self._ticker(locator, formatter)
		if self.orientation == 'vertical':

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efiringMar 18, 2018•
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You can use the long_axis, short_axis here, too. Initialize them prior to the_use_auto_colorbar_locator check.
Instead ofax.set_yticklabels you can use the equivalentshort_axis.set_ticklabels, etc.

jklymak force-pushed theenh-colorbar-ticks branch from2c33640 to252ef97Compare

March 18, 2018 15:23

ENH: colorbar ticks adjustable to colorbar size

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jklymak force-pushed theenh-colorbar-ticks branch from6bdc427 to52e5d81Compare

March 18, 2018 16:01

efiring approved these changes

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anntzer reviewed

Mar 19, 2018

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doc/api/api_changes/2017-12-01-JMK.rst Outdated


		Colorbar ticks now adjust for the size of the colorbar if the
		colorbar is made from a mappable that is not a contour or
		doesn't have a BoundaryNorm, or boundaries are not specified.

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extra space

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Mar 19, 2018

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lib/matplotlib/colorbar.py Outdated


		def __init__(self, colorbar):
		"""
		_ColorbarAutoLocator(colorbar)

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Is there a particular need to include the signature?

jklymak commented

Mar 19, 2018

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lib/matplotlib/colorbar.py Outdated

		if type(self.norm) == colors.LogNorm:
		long_axis.set_minor_locator(_ColorbarLogLocator(self,
		base=10., subs='auto'))
		long_axis.set_minor_formatter(ticker.NullFormatter())

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jklymakMar 19, 2018

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Need to check that some ticks are labelled...

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jklymakMar 19, 2018

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Fixed. LogLocator works fine here.

FIX: add loglocator for minor colorbar

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Mar 19, 2018

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afvincent commentedMar 21, 2018

@jklymak Is there an obvious reason why the ticks of the colorbar in the bottom right panel are not symmetrical (in log space) around 1 (e.g. [1e3, 1e0, 1e-3], instead of [1e2, 1e-1]), while the old one were “quite” symmetrical?

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jklymak commentedMar 21, 2018

@afvincent because the LogLocator only returned two tick marks as being able to fit and it chose those? Its just using the default LogLocator - i.e. if you had a normal yaxis that size, those are the ticks you'd get.

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Mar 22, 2018

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dopplershift merged commitdbfc79c intomatplotlib:master

Mar 22, 2018

Dih5 mentioned this pull request

Mar 23, 2018

Minor ticks on log-scale colorbar are not cleared#8358

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Mar 23, 2018

This was referencedSep 18, 2018

Incorrect placement of Colorbar ticks using LogNorm#12155

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FIX: colorbar re-check norm before draw for autolabels#12159

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anntzer mentioned this pull request

Oct 12, 2018

inconsistent colorbar tick labels for LogNorm#12488

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anntzer commentedOct 12, 2018

@skotaro Are you still interested in including your (extensive!) colorbar tutorial into the mpl docs? Even if it needs to be updated following this PR and/or to take constrained_layout into account, feel free to open an early issue/PR to track the work.