How to add border to bars and arcs

[mcp292]

Question

Is there a way to add a black border to bar and arc charts similar to this:

MWE

import pandas as pd
import altair as alt

source = pd.DataFrame({"category": [1, 2, 3, 4, 5, 6], "value": [4, 6, 10, 3, 7, 8]})

alt.Chart(source).mark_arc().encode(
    theta=alt.Theta(field="value", type="quantitative"),
    color=alt.Color(field="category", type="nominal"),
)

[jonmmease]

Yes, you can use the stroke and strokeWidth arguments to mark_arc:

import pandas as pd
import altair as alt

source = pd.DataFrame({"category": [1, 2, 3, 4, 5, 6], "value": [4, 6, 10, 3, 7, 8]})

alt.Chart(source).mark_arc(stroke="black", strokeWidth=3).encode(
    theta=alt.Theta(field="value", type="quantitative"),
    color=alt.Color(field="category", type="nominal"),
)

Hope that helps!

[mcp292]

Outstanding thank you!