[FEAT] Alternate chart colour schemes

ADBond commented 1 year ago

Is your proposal related to a problem?

Quite a few of our charts are using red-green scales, which is not great for colourblindness accessibility.

Describe the solution you'd like

Charts using other, more accessible, schemes that still convey the relevant information clearly - e.g. viridis (see https://github.com/moj-analytical-services/splink/issues/1437#issuecomment-1634924919), brewer,

Might also be nice to have a few options - a sensible default, maybe a couple of other options, and perhaps the option for custom user-specified schemes.

Describe alternatives you've considered

Additional context

Loosely related: #642.

samnlindsay commented 1 year ago

A thought that occurred while looking at #1578

[!NOTE] Just while I'm testing out the new alert blockquote feature, I wonder if the colour issue could be addressed by adding a property to the linker that toggles required accessibility adjustments. So something like linker.accessible_charts = True can be set and the charts contain something like
if linker.accessible_charts:
  chart_def[...][...]["color"]["scale"] = diverging_colours_accessible
else:
  chart_def[...][...]["color"]["scale"] = diverging_colours_default
Where the colour scales (and likewise any other formatting) can be stored centrally and imported

Given the vast array of charts, it's difficult to ensure consistency of style across the board, whether performing one-off changes or more crucially when attempting to provide multiple options to users.

Aside from the color scheme, various formatting choices can and probably should be standardised, with or without additional options:

Font sizes (title, axis title, axis labels)
- options for user to larger/smaller text variants (e.g. linker.profile_columns(text_size = "large") or a global linker.text_size = "large")
Color scales (global default continuous scale for match_probability and diverging scale for match_weight)
- options for alternatives (e.g. linker.match_weights_chart(monochrome=True))
- dark-mode charts with dark background (linker.dark_mode=True)

RossKen commented 1 year ago

Good pair programming use case

RobinL commented 1 year ago

There is such a thing as a vega lite theme. I wonder whether it could be used to blanket apply some styles. (I've never tried it)

samnlindsay commented 1 year ago

https://github.com/vega/vega-themes

https://observablehq.com/@vega/vega-themes-demo

A demo of using a custom theme with altair is shown here:

theme defined here

import altair as alt
from ... import theme

alt.themes.register('splink_theme', theme)
alt.themes.enable('splink_theme')

moj-analytical-services / splink