observablehq / observablehq/plot

Cumulative group?

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enhancement
Dominant language
HTML
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Description

I think the group transform could support a cumulative option, as the bin transform does. It’s less rarely needed since group is sometimes used with a categorical dimension, but it should make sense with an ordinal dimension.

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Research direction

Start by comparing the existing group and bin transforms, especially how bin handles a cumulative option. Clarify the intended behavior for ordinal dimensions and define what the cumulative group output should be before implementing it; done means the option works consistently without changing categorical grouping unexpectedly.

Written by the indexing model from the issue text.

Assessment

Tech stack
d3
Domain
data-visualization
Issue type
Feature
Difficulty
5/5
Estimated time
Over a week
Activity status
Stale
Clarity
Needs clarification
Newbie friendliness
25/100

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