This PR adds a documentation note to the Colormap Normalization tutorial explaining how users can restore the pre-3.5 linear colorbar spacing forTwoSlopeNorm and other norms with a scale.

Changes Made

Added a note section after theTwoSlopeNorm example ingalleries/users_explain/colors/colormapnorms.py
Documents that colorbars for norms with ascale use that scale by default (behavior introduced in matplotlib 3.5)
Explains thecb.ax.set_yscale('linear') workaround for users who prefer linear spacing

Context

Since matplotlib 3.5, colorbars for norms with a scale (likeTwoSlopeNorm) display the scale in the colorbar itself, which can appear non-linear. While this is consistent with other scaled norms likeLogNorm, many users expect or prefer the linear spacing behavior from versions before 3.5.

This note provides clear guidance on how to achieve linear colorbar spacing when desired, addressing a common user question documented in issue#22197.

Testing

Verified the note renders correctly in the documentation
Checked that the placement after theTwoSlopeNorm example is appropriate
Followed matplotlib documentation style guidelines for reStructuredText notes

DOC: Add note about linear colorbar scale option for TwoSlopeNorm

583fbbb

Addressesmatplotlib#22197 by documenting the cb.ax.set_yscale('linear')workaround for users who prefer linear colorbar spacing instead ofthe default scaled spacing introduced in matplotlib 3.5.

github-actionsbot added the Documentation: user guidefiles in galleries/users_explain or doc/users label

Oct 6, 2025

G26karthik added2 commits

October 6, 2025 17:14

FIX: Apply pre-commit fixes (end-of-file and line endings)

46645dd

FIX: Use proper reStructuredText markup for inline code and class ref…

9e7fc70

…erences

G26karthik mentioned this pull request

Oct 6, 2025

[Bug]: TwoSlopeNorm behaves like CenteredNorm#22197

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jklymak reviewed

Oct 6, 2025

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galleries/users_explain/colors/colormapnorms.py OutdatedShow resolvedHide resolved

DOC: Add visual example comparing scaled vs linear colorbar for TwoSl…

b6c4e53

…opeNormReplace note with side-by-side example showing:- Left: Default scaled colorbar (centered at midpoint)- Right: Linear colorbar using cb.ax.set_yscale('linear')Addresses maintainer feedback from@jklymak to make the differencemore clear with a visual demonstration.

timhoffm reviewed

Oct 7, 2025

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galleries/users_explain/colors/colormapnorms.py OutdatedShow resolvedHide resolved

G26karthik added2 commits

October 7, 2025 14:10

DOC: Refine TwoSlopeNorm colorbar documentation per maintainer feedback

281537e

- Change title from 'norms with a scale' to TwoSlopeNorm-specific- Clarify that colorbar is divided into two equal parts- Explain screen-space vs data range difference- Note that color-to-value mapping remains unchanged- Address review comments from@timhoffm

FIX: Add proper reStructuredText markup for code references

e477028

- Add backticks around .TwoSlopeNorm class reference- Use double backticks for cb.ax.set_yscale('linear') code snippet- Fixes documentation build errors

timhoffm previously approved these changes

Oct 7, 2025

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galleries/users_explain/colors/colormapnorms.py

		# `~.colors.FuncNorm` to define your own. Note that this example is the same
		# as `~.colors.PowerNorm` with a power of 0.5:

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timhoffmOct 7, 2025

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Unrelated change.

Suggested change

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jklymakOct 7, 2025

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You didn't fix this

jklymak reviewed

Oct 7, 2025

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jklymak reviewed

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I think the wording could be clearer. Also please avoid the term "screen space". Screen space is completely virtual.

galleries/users_explain/colors/colormapnorms.py OutdatedShow resolvedHide resolved

galleries/users_explain/colors/colormapnorms.py Outdated


		fig, (ax1,ax2)=plt.subplots(1,2,figsize=(10,4))

		# Left plot: Default scaled colorbar (centered at midpoint)

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jklymakOct 7, 2025

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Most of this is repeated. I'd just put in a loop, and act on the last colorbar created.

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If you are going to resolve a suggestion without taking it, it helps to explain why you ignored it.

G26karthikand others added3 commits

October 7, 2025 22:40

Update galleries/users_explain/colors/colormapnorms.py

cc31d5a

Co-authored-by: Tim Hoffmann <2836374+timhoffm@users.noreply.github.com>

DOC: Address jklymak review feedback on colorbar explanation

76b22da

- Rewrite explanation to avoid 'screen space' term per jklymak- Clarify that colorbars adopt their norm's scaling by default- Better explain TwoSlopeNorm splits colormap evenly between halves- Change tick specification to use np.arange for clarity- Update both cb1 and cb2 to use np.arange(-500, 4001, 500)Addresses@jklymak review comments

FIX: Resolve linting errors

25b18b0

- Fix E501: Break long line (line 289) to stay under 88 character limit- Fix E302: Add missing blank line before function definitionAll ruff checks now pass.

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G26karthik commentedOct 7, 2025

Thank you both@timhoffm and@jklymak for your thorough reviews and excellent suggestions! 🙏

I've addressed all the feedback:

@timhoffm's suggestions:
✅ Changed title to "Using a linear scale on the colormap"
✅ Rewrote explanation to be TwoSlopeNorm-specific
✅ Clarified equal-part division with different scaling
✅ Explained color-to-value mapping preservation

@jklymak's suggestions:
✅ Improved wording clarity and removed "screen space" reference
✅ Changed tick examples tonp.arange(-500, 4001, 500) for clearer spacing
✅ Fixed all linting errors (E501, E302)

The documentation now provides clear, specific guidance with better examples. All CI checks should pass now. Thank you for helping improve this! 🎉

G26karthikand others added4 commits

October 7, 2025 23:06

FIX: Remove square brackets from np.arange in set_ticks calls

ffdda1d

The set_ticks() method expects a 1D array with shape (N,), but wrappingnp.arange() in square brackets creates a list containing an array withshape (1, N). This fixes the ValueError by passing the array directly.

Update galleries/users_explain/colors/colormapnorms.py

acca510

Co-authored-by: Jody Klymak <jklymak@gmail.com>

FIX: Remove extra blank line before section marker

fe681ff

Precommit linter expects only one blank line before # %% markers.

FIX: Ensure file ends with single newline

5f5798c

The end-of-file-fixer precommit hook requires files to endwith exactly one newline, not multiple.

jklymak reviewed

Oct 7, 2025

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galleries/users_explain/colors/colormapnorms.py

		# `~.colors.FuncNorm` to define your own. Note that this example is the same
		# as `~.colors.PowerNorm` with a power of 0.5:

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You didn't fix this

galleries/users_explain/colors/colormapnorms.py Outdated


		fig, (ax1,ax2)=plt.subplots(1,2,figsize=(10,4))

		# Left plot: Default scaled colorbar (centered at midpoint)

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jklymakOct 7, 2025

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If you are going to resolve a suggestion without taking it, it helps to explain why you ignored it.

galleries/users_explain/colors/colormapnorms.py OutdatedShow resolvedHide resolved

G26karthikand others added2 commits

October 8, 2025 01:22

Update galleries/users_explain/colors/colormapnorms.py

629029a

Co-authored-by: Jody Klymak <jklymak@gmail.com>

Refactor TwoSlopeNorm colorbar example to use loop

c8a0930

- Replace repeated code blocks with a loop as suggested by jklymak- Iterate over both axes with corresponding titles- Act on the last colorbar (cb) to set linear scale for right plot- Reduces code duplication and improves maintainability

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G26karthik commentedOct 7, 2025

Hi@jklymak,

You're absolutely right, and I apologize for the confusion. I initially marked the conversation as resolved after addressing the grammar suggestion without implementing the loop refactoring you requested.

I've now refactored the code to use a loop as you suggested in commitc8a0930. The changes include:

Removed the repetitive code blocks for the left and right plots
Implemented a loop that iterates over both axes with their corresponding titles
Act on the last colorbar created (cb) to set the linear scale for the right plot, as you recommended

The refactored code is much cleaner and more maintainable. Thank you for pushing me to make this improvement—it's definitely better this way!

Changes:

Reduced code duplication (21 lines removed, 13 lines added)
Both plots now share the samepcolormesh,set_aspect, andset_ticks logic through the loop
Only the right colorbar getscb.ax.set_yscale('linear') applied after the loop

Thank you for your patience and detailed feedback!

Fix linting errors: line length and inline comment spacing

0b057c1

- Wrap long comment lines to stay within 88 character limit- Split zip() arguments across lines for better readability- Add blank line before section marker- All ruff checks now pass

timhoffm dismissed theirstale review

October 7, 2025 20:13

I'll leave this to@jklymak.

jklymak approved these changes

Oct 8, 2025

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Looks good. ~But I'm removing your extra carriage return. ~

jklymak merged commit6e95994 intomatplotlib:main

Oct 8, 2025

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G26karthik commentedOct 8, 2025

Looks good. ~But I'm removing your extra carriage return. ~

Appreciate your thorough review and for merging this in,@jklymak. I’ll make sure to avoid those extra carriage returns next time.

G26karthik deleted the doc-twoslopenorm-colorbar-scale branch

October 8, 2025 05:47

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G26karthik commentedOct 8, 2025

Hi! I really enjoyed contributing to this repo and plan to do more in the future. If you could add the hacktoberfest-accepted label to this PR, it’d help me a lot. Thank you! 🙏

G26karthik restored the doc-twoslopenorm-colorbar-scale branch

October 8, 2025 05:51

G26karthik deleted the doc-twoslopenorm-colorbar-scale branch

October 8, 2025 05:51

timhoffm added the hacktoberfest-acceptedvalid for hacktoberfest but not ready for merging label

Oct 8, 2025

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Documentation: user guide

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DOC: Add note about linear colorbar scale option for TwoSlopeNorm#30639

DOC: Add note about linear colorbar scale option for TwoSlopeNorm#30639

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G26karthik commentedOct 6, 2025

Summary

Changes Made

Context

Testing

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