Horizontal Stripplot with Jitter using Altair in Python

In this post, we will learn how to make horizontal stripplot with jitter using Altair in Python. In an earlier post we learned step-by-step instructions to make stripplot with jitter.

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

We will use gapminder dataset to make the stripplot with Altair. Let us load the data from web using Pandas’s read_csv() function.

data_url = 'http://bit.ly/2cLzoxH'
gapminder = pd.read_csv(data_url)
gapminder.head()

	country	year	pop	continent	lifeExp	gdpPercap
0	Afghanistan	1952	8425333.0	Asia	28.801	779.445314
1	Afghanistan	1957	9240934.0	Asia	30.332	820.853030
2	Afghanistan	1962	10267083.0	Asia	31.997	853.100710
3	Afghanistan	1967	11537966.0	Asia	34.020	836.197138
4	Afghanistan	1972	13079460.0	Asia	36.088	739.981106

We will primarily follow the code for stripplot with jitter with one big change that is we swap our x and y-axis variables. In the code for horizontal stripplot, our x-axis is lifeExp and y-axis is the jitter.

horizontal_stripplot =  alt.Chart(gapminder, width=600, height=100).mark_circle(size=12).encode(
    y=alt.Y(
        'jitter:Q',
        title=None,
        axis=alt.Axis(values=[0], ticks=True, grid=False, labels=False),
        scale=alt.Scale(),
    ),
    x=alt.X('lifeExp:Q', scale=alt.Scale(domain=(20, 85))),
    color=alt.Color('continent:N', legend=None),
    row=alt.Row(
        'continent:N',
        header=alt.Header(
            labelAngle=0,
            labelFontSize=16,
            titleOrient='top',
            labelOrient='left',
            labelAlign='left',
        ),
    ),
).transform_calculate(
    # Generate Gaussian jitter with a Box-Muller transform
    jitter='sqrt(-2*log(random()))*cos(2*PI*random())'
).configure_facet(
    spacing=0
).configure_view(
    stroke=None
).configure_axis(
    labelFontSize=16,
    titleFontSize=16
)

We can use the Altair plot object to visualize the horizontal strippplot.

horizontal_stripplot

We have a nice horizontal stripplot with jitter as we needed.