.. This document is auto-generated by the altair-gallery extension. Do not modify directly.

.. _gallery_interactive_legend:


Interactive Legend
------------------
The following shows how to create a chart with an interactive legend, by
binding the selection to ``"legend"``. Such a binding only works with
``selection_single`` or ``selection_multi`` when projected over a single
field or encoding.


.. altair-plot::
    :code-below:

    
    import altair as alt
    from vega_datasets import data

    source = data.unemployment_across_industries.url

    selection = alt.selection_multi(fields=['series'], bind='legend')

    alt.Chart(source).mark_area().encode(
        alt.X('yearmonth(date):T', axis=alt.Axis(domain=False, format='%Y', tickSize=0)),
        alt.Y('sum(count):Q', stack='center', axis=None),
        alt.Color('series:N', scale=alt.Scale(scheme='category20b')),
        opacity=alt.condition(selection, alt.value(1), alt.value(0.2))
    ).add_selection(
        selection
    )

.. toctree::
   :hidden: