runtime/Lib/site-packages/altair/examples/histogram_responsive.py

"""
Histogram with Responsive Bins
------------------------------
This shows an example of a histogram with bins that are responsive to a
selection domain. Click and drag on the bottom panel to see the bins
change on the top panel.
"""
# category: histograms
import altair as alt
from vega_datasets import data

source = data.flights_5k.url

brush = alt.selection_interval(encodings=['x'])

base = alt.Chart(source).transform_calculate(
    time="hours(datum.date) + minutes(datum.date) / 60"
).mark_bar().encode(
    y='count():Q'
).properties(
    width=600,
    height=100
)

alt.vconcat(
  base.encode(
    alt.X('time:Q',
      bin=alt.Bin(maxbins=30, extent=brush),
      scale=alt.Scale(domain=brush)
    )
  ),
  base.encode(
    alt.X('time:Q', bin=alt.Bin(maxbins=30)),
  ).add_selection(brush)
)