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

.. _gallery_layered_histogram:


Layered Histogram
=================
This example shows how to use opacity to make a layered histogram in Altair.


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

    
    import pandas as pd
    import altair as alt
    import numpy as np
    np.random.seed(42)

    # Generating Data
    df = pd.DataFrame({'Trial A': np.random.normal(0, 0.8, 1000),
                       'Trial B': np.random.normal(-2, 1, 1000),
                       'Trial C': np.random.normal(3, 2, 1000)})

    # Tidying Data
    df = pd.melt(df, id_vars=df.index.name,
                 value_vars=df.columns,
                 var_name='Experiment',
                 value_name='Measurement')

    alt.Chart(df).mark_area(
        opacity=0.3,
        interpolate='step'
    ).encode(
        alt.X('Measurement', bin=alt.Bin(maxbins=100)),
        alt.Y('count()', stack=None),
        alt.Color(
            'Experiment',
            scale=alt.Scale(range=['#0000ff', '#008000', '#ff0000'])
        )
    )


.. toctree::
   :hidden: