WIP: Add offset normalizer #3858

phobson · 2014-11-27T16:31:23Z

Trying to close #1806

Not currently on a good machine for development, but I think this pretty straight-forward, so hopefully Travis a test runner will suffice...

OffsetNorm: This let's you set vmin, vcenter, and vmax. The use case for this is when you have data ranging from e.g., -1, to +2, and you want the the white/gray part at 0, but would also like to use the full range of the red scale. So:

offset = mcolors.OffsetNorm(vmin=-1, vcenter=0, vmax=2)
offset([-1.0, -0.5, 0.0, 1.0, 2.,])

#prints
[0, 0.25, 0.5, 0.75, 1.0]

Next I'll add SymNorm, that will look at the absolute values of vmin and vmax to produce:

sym = mcolors.SymNorm(vmin=-1, vcenter=0, vmax=2)
sym([-1.0, -0.5, 0.0, 1.0, 2.,])

#prints
[0.25, 0.325, 0.5, 0.75, 1.0]

phobson · 2014-11-27T16:35:48Z

@tacaswell I based this off of a master that I pulled down last night. Is that ok?

tacaswell · 2014-11-27T16:42:04Z

Yes

On Thu, Nov 27, 2014, 11:35 Paul Hobson notifications@github.com wrote:

@tacaswell https://github.com/tacaswell I based this off of a master
that I pulled down last night. Is that ok?

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#3858 (comment)
.

Tillsten · 2014-11-28T01:10:32Z

You are right about my last comment, but i have still three points:
There is buggy behavior with all negative limits:

os = OffsetNorm(-5, -2, -1)
x = np.linspace(-6, 6, 100)
abs(x-os.inverse(os(x))).max()  #should be zero, but is two

This is why my stackoverflow answer (which you probably read before :)) divides by

 abs(vmax - midpoint) 
 abs(vmin - midpoint)

instead of vmax-vcenter.

Second point the class has no docstring.
Third is i don't think OffsetNorm is a very descriptive name, but the alternatives are also not
very good (MidpointNorm, CenteredNorm) .

phobson · 2014-11-28T01:13:28Z

Yeah. Good points all around. What you you think about BiasedNorm?

tacaswell · 2014-11-29T22:06:05Z

lib/matplotlib/colors.py

+            raise ValueError("Not invertible until scaled")
+
+        vmin = float(self.vmin)
+        vcenter = float(self.vcenter)


I think there is a code path that will end up with self.vcenter to be None? I think you need to also override autoscale_None to make sure it gets set.

@tacaswell yup. Got that written, Will default to half-way in the middle if not specified.

Thought about looking at the signs of vmax and vmin to see if 0 would be a good choice, but I think edge cases of -0.001 and 1000 make that more complicated than it means to be,

tacaswell · 2014-11-29T22:09:33Z

Needs documentation and tests that stress the code a bit more.

phobson · 2014-11-30T05:09:53Z

Hey @Tillsten

I really feel like your class you posted on SO is more robust. I don't feel right using it here without you on the commit log. Do you want to pull this branch down and overwrite what I have with your class?

phobson · 2014-11-30T05:20:29Z

@tacaswell

About the tests, happy to beef things about a bit. What do you think about the pattern I'm using with subclassing a base test case? I feel like the whole file could benefit from similar treatment (separate PR,of course).

phobson · 2014-11-30T05:48:16Z

Here's that SO solution from @Tillsten
http://stackoverflow.com/questions/7404116/defining-the-midpoint-of-a-colormap-in-matplotlib/7746125#7746125

Tillsten · 2014-11-30T20:36:34Z

@phobsen Just use it, i will hopefully get other commits anyway. If i ever find the free time ... :)

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

tacaswell · 2014-12-12T05:13:47Z

lib/matplotlib/colors.py

+        self.vmax = vmax
+        self.clip = clip
+
+    def __call__(self, value, clip=False):


Should the default value be None ?

tacaswell · 2014-12-12T05:19:32Z

This looks pretty solid. Left a few picky comments.

I am a bit confused by the decorators working on 2.6 and a bit concerned about the test classes as I don't recall seeing them anyplace else in the test suite.

phobson · 2015-06-15T20:13:36Z

I did. It didn't change anything, though I was working on a janky dev installation of MPL, so I should probably give it another shot.

Looking back a existing source code, LogNorm does have an inverse method, so there's something to learn there I'm sure.

OceanWolf · 2015-06-30T00:24:37Z

Just had an idea in terms of a name for the general case, GraduatedNorm, what do you think?

efiring · 2015-06-30T18:54:08Z

It sounds like all this is actually about using a continuous piece-wise linear curve (first-degree spline) as the mapping function. Is that correct? GraduatedNorm doesn't give me any picture of what it is supposed to be.

Tillsten · 2015-07-01T03:17:09Z

PiecewiseLinearNorm sounds good to me.

WeatherGod · 2015-07-01T14:32:10Z

I like that name.

On Tue, Jun 30, 2015 at 11:17 PM, Till Stensitzki notifications@github.com
wrote:

PiecewiseLinearNorm sounds good to me.

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#3858 (comment)
.

OceanWolf · 2015-07-01T14:33:52Z

👍

tacaswell · 2015-07-16T04:20:05Z

Closing in favor of #4666 @phobson ping to have this re-opened if you want to take over development again.

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858`

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst DOC: add tutorial FIX: fix extend=both

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst DOC: add tutorial FIX: fix extend=both

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst DOC: add tutorial FIX: fix extend=both DOC: add new example

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst DOC: add tutorial FIX: fix extend=both DOC: add new example

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: https://github.com/matplotlib/matplotlib/pull/3858` TST: add tests for DivergingNorm DOC: add to colors_api.rst DOC: add tutorial FIX: fix extend=both DOC: add new example

tacaswell added the status: needs review label Nov 27, 2014

phobson mentioned this pull request Nov 27, 2014

Add symmetric norm for colormaps #1806

Closed

phobson force-pushed the add-asym-norm branch 2 times, most recently from 60aaec1 to 37ff5a5 Compare November 27, 2014 21:32

tacaswell added status: needs revision and removed status: needs review labels Nov 29, 2014

tacaswell added this to the v1.5.x milestone Nov 29, 2014

tacaswell reviewed Nov 29, 2014
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phobson force-pushed the add-asym-norm branch from 2d41664 to 933626c Compare December 1, 2014 08:18

phobson force-pushed the add-asym-norm branch from 933626c to 0b17fcf Compare December 1, 2014 17:00

phobson force-pushed the add-asym-norm branch from 0b17fcf to 205e8b9 Compare December 1, 2014 18:28

tacaswell added status: needs review and removed status: needs revision labels Dec 12, 2014

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dopplershift mentioned this pull request Jul 11, 2015

Add PiecewiseLinearNorm #4666

Closed

tacaswell closed this Jul 16, 2015

tacaswell removed the status: needs review label Jul 16, 2015

phobson deleted the add-asym-norm branch October 14, 2016 17:03

jklymak mentioned this pull request Oct 6, 2018

Add DivergingNorm (again, again, again) #12419

Merged

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ImportanceOfBeingErnest mentioned this pull request Sep 26, 2019

DivergingNorm is a misleading name #15336

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WIP: Add offset normalizer #3858

WIP: Add offset normalizer #3858

phobson commented Nov 27, 2014

phobson commented Nov 27, 2014

tacaswell commented Nov 27, 2014

Tillsten commented Nov 28, 2014

phobson commented Nov 28, 2014

tacaswell Nov 29, 2014

phobson Nov 30, 2014

tacaswell commented Nov 29, 2014

phobson commented Nov 30, 2014

phobson commented Nov 30, 2014

phobson commented Nov 30, 2014

Tillsten commented Nov 30, 2014

tacaswell Dec 12, 2014

tacaswell commented Dec 12, 2014

phobson commented Jun 15, 2015

OceanWolf commented Jun 30, 2015

efiring commented Jun 30, 2015

Tillsten commented Jul 1, 2015

WeatherGod commented Jul 1, 2015

OceanWolf commented Jul 1, 2015

tacaswell commented Jul 16, 2015

WIP: Add offset normalizer #3858

WIP: Add offset normalizer #3858

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phobson commented Nov 27, 2014

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