Altair

Altair is a declarative statistical visualization library for python.

This document can be compiled to html with

```
stitch ex_altair.txt -o ex_altair.html --no-self-contained
```
In [1]: from altair import Chart, load_dataset
   ...: from IPython import display
   ...:
   ...: # load data as a pandas DataFrame
   ...: cars = load_dataset('cars')
   ...:
   ...: c = Chart(cars).mark_point().encode(
   ...:     x='Horsepower',
   ...:     y='Miles_per_Gallon',
   ...:     color='Origin'
   ...: )
   ...: c
In [2]: display.HTML(c.to_html())
Vega-Lite Chart