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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Reply to this email directly or view it on GitHub
#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 · 2014-11-29T22:08:24Z

lib/matplotlib/colors.py

+
+
+class SymmetricalNorm(Normalize):
+    def __init__(self, vmin=None, vmax=None, clip=False):


I am not really a fan of this class. It will also behave in very strange ways for vmin/vmax of the same sign.

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 ... :)


        ENH: Add OffsetNorm and tests

@Tillsen

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


        ENH: Add OffsetNorm and tests

@Tillsen

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


        ENH: Add OffsetNorm and tests

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: matplotlib#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 · 2014-12-12T05:15:42Z

lib/matplotlib/colors.py

+        if self.vcenter is None:
+            self.vcenter = (self.vmax + self.vmin) * 0.5
+
+        return None


Don't need the return

tacaswell · 2014-12-12T05:18:01Z

lib/matplotlib/tests/test_colors.py

+    def setup(self):
+        self.vals = np.arange(50)
+
+    @nt.raises(ValueError)


~~How are these passing on 2.6? I thought the decorator-style raise tests are not available until 2.7...~~ nm, I was confused

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.


        ENH: Add OffsetNorm and tests

@Tillsen

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


        ENH: Add OffsetNorm and tests

@Tillsen

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


        ENH: Add OffsetNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

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


        ENH: Add PiecewiseLinearNorm and tests

@Tillsen

Borrows heavily from @Tillsen's solution found on StackOverflow here: http://goo.gl/RPXMYB Used with his permission dicussesd on Github here: matplotlib#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 Needs review label Nov 27, 2014

phobson mentioned this pull request Nov 27, 2014

Add symmetric norm for colormaps #1806

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tacaswell added Needs revision and removed Needs review labels Nov 29, 2014

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phobson force-pushed the phobson:add-asym-norm branch from 2d41664 to 933626c Dec 1, 2014

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tacaswell added Needs review and removed Needs revision labels Dec 12, 2014

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lib/matplotlib/colors.py Outdated

self.vmax = vmax

self.clip = clip

def __call__(self, value, clip=False):

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tacaswell Dec 12, 2014
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Should the default value be None ?

tacaswell reviewed Dec 12, 2014
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lib/matplotlib/colors.py Outdated

if self.vcenter is None:

self.vcenter = (self.vmax + self.vmin) * 0.5

return None

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tacaswell Dec 12, 2014
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Don't need the return

tacaswell reviewed Dec 12, 2014
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dopplershift mentioned this pull request Jul 11, 2015

Add PiecewiseLinearNorm #4666

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tacaswell closed this Jul 16, 2015

tacaswell removed the Needs review label Jul 16, 2015

jkseppan added a commit to jkseppan/matplotlib that referenced this pull request Sep 13, 2015

ENH: Add OffsetNorm and tests

92bc85b

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

OceanWolf added a commit to OceanWolf/matplotlib that referenced this pull request Sep 14, 2015

ENH: Add OffsetNorm and tests

05c1b76

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

phobson deleted the phobson:add-asym-norm branch Oct 14, 2016

jklymak added a commit to jklymak/matplotlib that referenced this pull request Oct 6, 2018

ENH: Add OffsetNorm and tests

798baf9

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

jklymak mentioned this pull request Oct 6, 2018

Add DivergingNorm (again, again, again) #12419

Merged

3 of 6 tasks complete

ImportanceOfBeingErnest mentioned this pull request Sep 26, 2019

DivergingNorm is a misleading name #15336

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WIP: Add offset normalizer #3858

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