Is there a way to customize the colors of a selection detail chart in Altair?

Question

I have been playing around with the following selection detail example from the Altair gallery, as I think I would like to do something similar with some data I have:

https://altair-viz.github.io/gallery/select_detail.html

However, I am wondering if there is a way to make it so that all the points and lines are a uniform color, because the redundant encoding feels confusing to me. So far, I have not been able to come up with a way to do this. I can change the color scale using alt.Color, but I am unsure how to specify there to be just one color total.

Answer 1

You can use the detail encoding to group observations without assigning them a visual attribute:

points = base.mark_point(filled=True, size=200).encode(
    x='mean(x)',
    y='mean(y)',
    detail='id:O',
    opacity=alt.condition(selector, alt.value(1), alt.value(0.2)),
)

timeseries = base.mark_line().encode(
    x='time',
    y=alt.Y('value', scale=alt.Scale(domain=(-15, 15))),
    detail='id:O',
).transform_filter(
    selector
)

points | timeseries