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

.. _gallery_scatter_with_histogram:


Scatter Plot and Histogram with Interval Selection
==================================================

This example shows how to link a scatter plot and a histogram
together such that an interval selection in the histogram will
plot the selected values in the scatter plot.

Note that both subplots need to know about the `mbin` field created
by the `transform_bin` method. In order to achieve this, the data is
not passed to the `Chart()` instances creating the subplots, but
directly in the `hconcat()` function, which joins the two plots together.


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

    

    import altair as alt
    import pandas as pd
    import numpy as np

    x = np.random.normal(size=100)
    y = np.random.normal(size=100)

    m = np.random.normal(15, 1, size=100)

    source = pd.DataFrame({"x": x, "y":y, "m":m})

    # interval selection in the scatter plot
    pts = alt.selection(type="interval", encodings=["x"])

    # left panel: scatter plot
    points = alt.Chart().mark_point(filled=True, color="black").encode(
        x='x',
        y='y'
    ).transform_filter(
        pts
    ).properties(
        width=300,
        height=300
    )

    # right panel: histogram
    mag = alt.Chart().mark_bar().encode(
        x='mbin:N',
        y="count()",
        color=alt.condition(pts, alt.value("black"), alt.value("lightgray"))
    ).properties(
        width=300,
        height=300
    ).add_selection(pts)

    # build the chart:
    alt.hconcat(
        points,
        mag,
        data=source
    ).transform_bin(
        "mbin",
        field="m",
        bin=alt.Bin(maxbins=20)
    )


.. toctree::
   :hidden: