Appending a new mark after Plot.plot has been called

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1

Is there a way to add a new mark to a Plot after it has been created?

More broadly, I have a few lines I want to display, but only one of the lines (call this the prediction line) will be displayed when the pointer moves across the chart. I want to be able to only display the prediction line to the right of pointerX.

I imagine one option will be to use the input EventListener to feed into a callback that can dynamically filter what should be displayed for the prediction line, but this would require being able to also append a Plot.line mark in the callback.

I hope this is clear! Any help is much appreciated, thanks in advance!

2

It’s not possible to add marks after the chart is rendered, but here are two ways to do what you want:

  1. create the mark initially, and use the render option to display it later (interactively); or
  2. create the line as a new path in the generated SVG, possibly building on the scales to make it consistent with the other marks.

See document the custom render option by Fil · Pull Request #1811 · observablehq/plot · GitHub and Interactions | Observable Plot

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