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

.. _gallery_scatter_with_loess:


Scatter Plot with LOESS Lines
-----------------------------
This example shows how to add a trend line to a scatter plot using 
the LOESS transform (LOcally Estimated Scatterplot Smoothing).


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

    

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

    np.random.seed(1)

    source = pd.DataFrame({
        'x': np.arange(100),
        'A': np.random.randn(100).cumsum(),
        'B': np.random.randn(100).cumsum(),
        'C': np.random.randn(100).cumsum(),
    })

    base = alt.Chart(source).mark_circle(opacity=0.5).transform_fold(
        fold=['A', 'B', 'C'], 
        as_=['category', 'y']
    ).encode(
        alt.X('x:Q'), 
        alt.Y('y:Q'), 
        alt.Color('category:N')
    )

    base + base.transform_loess('x', 'y', groupby=['category']).mark_line(size=4)


.. toctree::
   :hidden: