# Kernel Density Estimation

Learn how to add kernel density estimation to an Altair chart.

## We'll cover the following

**Kernel density estimation (KDE)** is a statistical method used to estimate the probability density function of a random variable based on a set of observed data points. In simpler terms, KDE creates a smooth curve approximating the distribution of a dataset, which can help us better understand the underlying patterns and characteristics of the data.

## How to use KDE in Altair

Altair supports KDE by allowing us to plot a KDE line directly into an Altair plot. To plot KDE in Altair, we use the `transform_density()`

method. This function receives the following parameters as input:

The column of the dataset used for the density estimation

The

`as_`

parameter renames the new columns created after the transformation.

We can use the `transform_density()`

method with `mark_area()`

or `mark_line()`

.

## Let’s practice!

We’ll consider the following dataset:

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