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

.. _gallery_bar_chart_with_highlight:


Bar Chart with Highlight
------------------------
This example shows a Bar chart that highlights values beyond a threshold.


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

    
    import altair as alt
    import pandas as pd

    data = pd.DataFrame({"Day": range(1, 16),
                         "Value": [54.8, 112.1, 63.6, 37.6, 79.7, 137.9, 120.1, 103.3,
                                   394.8, 199.5, 72.3, 51.1, 112.0, 174.5, 130.5]})

    data2 = pd.DataFrame([{"ThresholdValue": 300, "Threshold": "hazardous"}])

    bar1 = alt.Chart(data).mark_bar().encode(
        x='Day:O',
        y='Value:Q'
    )

    bar2 = alt.Chart(data).mark_bar(color="#e45755").encode(
        x='Day:O',
        y='baseline:Q',
        y2='Value:Q'
    ).transform_filter(
        "datum.Value >= 300"
    ).transform_calculate(
        "baseline", "300"
    )

    rule = alt.Chart(data2).mark_rule().encode(
        y='ThresholdValue:Q'
    )

    text = alt.Chart(data2).mark_text(
        align='left', dx=215, dy=-5
    ).encode(
        alt.Y('ThresholdValue:Q', axis=alt.Axis(title='PM2.5 Value')),
        text=alt.value('hazardous')
    )

    bar1 + text + bar2 + rule


.. toctree::
   :hidden: