Adding titles to a grouped bar chart

[amandaha8]

What happened?

I'm using the dataset "source" in the grouped bar chart example. I'd like to add a title above the X-Axis title of "Category" that indicates this graph is grouped by the column "Group." However, when I edit the code following this page, no title pops up.

alt.Chart(source).mark_bar().encode(
    x="Category:N",
    y="Value:Q",
    xOffset=alt.X("Group:N", title = "Groups")
    color="Group:N"
)

What would you like to happen instead?

No response

Which version of Altair are you using?

'5.1.1'

[mattijn]

Thanks for reporting! This indeed seems like a mismatch between the documentation and the actual behavior. My gut-feeling is that the behavior is right and that the documentation should not include title as a valid option (through the jsonschema defintion). But this requires more investigation.

For now, you could use the following solution:

import altair as alt
import pandas as pd

source = pd.DataFrame({
    "Category":list("AAABBBCCC"),
    "Group":list("xyzxyzxyz"),
    "Value":[0.1, 0.6, 0.9, 0.7, 0.2, 1.1, 0.6, 0.1, 0.2]
})

alt.Chart(source).mark_bar().encode(
    x=alt.X("Category:N", title=["Categories", "Grouped by column 'Group'"]),
    y="Value:Q",
    xOffset=alt.XOffset("Group:N", title='this does not have impact'),
    color="Group:N"
)

Thanks again for the report!

[amandaha8]

Thank you for your help!