[Micro task] Update a Bokeh example plot

[pavithraes]

Select a Bokeh plot from the examples gallery, review it for accessibility (primarily, check the colors used in the plot), and update it to use more accessible colours if needed.

Share the plot you are working on a comment on this issue, so that we don't have multiple participants working on the same example.

You can make a PR against https://github.com/bokeh/bokeh/issues/11481 for this micro task to update plots. If you find plots that don't need updating, share it on this issue as a comment.

[BhaswatiRoy]

Hello @pavithraes I have changed the colors of Band Plot to more accessible colors with a good color contrast ratio https://github.com/bokeh/bokeh/pull/12922

[chinmaychahar]

Hi @pavithraes Updated examples/styling/mathtext/latex_schrodinger.py to a more accessible color palette referencing the docs.

#bokeh/bokeh/pull/12923

[Soot3]

Changed colorbar_log example from viridis to iridescent

#bokeh/bokeh/pull/12929

[robinokwanma]

Updated Color pallete for examples\plotting\histogram.py to be more visible and less conflicting

https://github.com/bokeh/bokeh/pull/12937

[AnishereMariam]

Updated colour palette data/linear_cmap.py.

[KesharwaniArpita]

hey , @pavithraes , @bryevdv i have changed the color of the jitter graph taken from the gallery. Can you review my work at https://github.com/KesharwaniArpita/outreach-programs/tree/Gallery_bokeh ?

[bryevdv]

Hi @KesharwaniArpita Thanks for the links. I am not sure that the new colors are an improvement according to the criteria of accessibility. One of the most common color deficiences is an inability to distinguish red from green, but these examples seem to be updated us use both those hues together. I think the jitter example may also have issues with low background/foreground contrast.

Here are some links that may be helpful:

• Bokeh's existing built-in accessible palettes (it would probably be best to try and select colors from these existing palettes) https://docs.bokeh.org/en/latest/docs/reference/palettes.html#accessible-palettes
• web contrast checker (you can check pairs of colors for decent contrast here, generally > 4.5 would be a good place to aim for https://webaim.org/resources/contrastchecker/
• General background info about color accessibility for data vis: https://xdgov.github.io/data-design-standards/components/colors

[Faith-Nchifor]

1. Link: https://docs.bokeh.org/en/latest/docs/examples/basic/bars/basic.html
2. https://docs.bokeh.org/en/latest/docs/examples/basic/areas/stacked_area.html Hello @pavithraes. I don't think these plots need updating. I think the bar plot is assessible enough even though it uses a default color. The palette (tol) used by the stacked area plot is assessible.

[Faith-Nchifor]

Hello mentors @bryevdv , @pavithraes. I have a question. I noticed that some colors in the example plots were generated using loops. For instance colors = np.array([(r, g, 150) for r, g in zip(50+2*x, 30+2*y)], dtype="uint8"). Does this exercise also involve replacing these colors with the color palettes even if the colors are already looking good?

[bryevdv]

Hi @Faith-Nchifor those are some very old examples that have also been used widely in various public project materials over the years. I think perhaps they could be improved, but I think it's not so clear cut and needs a more involved discussion. I'd advise looking at some of the other examples before those.

[Faith-Nchifor]

okay @bryevdv.

[Faith-Nchifor]

I worked on the slope plot https://github.com/bokeh/bokeh/pull/12959

[Soot3]

Saw some of those when I was trying out the examples. They all still work on the current version, while palettes like tol will output errors on older versions like bokeh-2.4.3 (which is the default in a Google Colab notebook)

Hi @Faith-Nchifor those are some very old examples that have also been used widely in various public project materials over the years. I think perhaps they could be improved, but I think it's not so clear cut and needs a more involved discussion. I'd advise looking at some of the other examples before those.

[fractaldatalearning]

Hello! I created a PR to make a small change to the span example in the gallery, changing from solid to dashed lines. TBH this is my first time making a PR to something other than a project between me and friends, so I’m very open to any feedback about the process as well as code.

[fractaldatalearning]

• Link: https://docs.bokeh.org/en/latest/docs/examples/basic/bars/basic.html
• https://docs.bokeh.org/en/latest/docs/examples/basic/areas/stacked_area.html I think the bar plot is assessible enough even though it uses a default color. The palette (tol) used by the stacked area plot is assessible.

Hi, In addition to these two, I went through the gallery and personally believe that the following examples may not require updating as they already have simple but clear descriptions, color combinations consistent with accessible palettes, and words that are legible and descriptive:

https://docs.bokeh.org/en/latest/docs/examples/basic/scatters/markers.html https://docs.bokeh.org/en/latest/docs/examples/basic/scatters/color_scatter.html https://docs.bokeh.org/en/latest/docs/examples/basic/scatters/elements.html https://docs.bokeh.org/en/latest/docs/examples/basic/data/transform_jitter.html https://docs.bokeh.org/en/latest/docs/examples/basic/axes/twin_axes.html https://docs.bokeh.org/en/latest/docs/examples/basic/bars/intervals.html https://docs.bokeh.org/en/latest/docs/examples/basic/bars/nested.html https://docs.bokeh.org/en/latest/docs/examples/basic/bars/colors.html https://docs.bokeh.org/en/latest/docs/examples/basic/layouts/anscombe.html https://docs.bokeh.org/en/latest/docs/examples/basic/annotations/whisker.html https://docs.bokeh.org/en/latest/docs/examples/basic/annotations/box_annotation.html

[bryevdv]

Thanks @fractaldatalearning jus FYI very many of the example plots have been updated in the repo but to not yet appear in the published gallery, because there has not yet been a new release since those changes. At this point, in order to see the true current state of the gallery, you would need to build the docs locally as described in the contributor guide.

[fractaldatalearning]

Thanks @fractaldatalearning jus FYI very many of the example plots have been updated in the repo but to not yet appear in the published gallery, because there has not yet been a new release since those changes. At this point, in order to see the true current state of the gallery, you would need to build the docs locally as described in the contributor guide.

Thanks for the clarification! It makes sense that there would actually be many more plots that are updated by now. To find any additional visualizations to work on, I’ll look through the repo.