CODEWITHSUNDEEP
pandasaltair
Juan
Juan

Reputation: 103

Stacked Bar-chart based on bool value column Altair

I'm trying to do something like below.

Group by the date column, for example year or year/month. And visualize a stacked bar chart, based on the True/False value.

What's the best way to go about this in Altair?

df = pd.DataFrame({
    'date': ['20-03-2017', '20-03-2017', '20-03-2018', '21-03-2018', '20-10-2019', '20-03-2019', '1-02-2019', '10-03-2020', '20-06-2020'],
    'value': [True, True, True, False, True, False, False, True, False]
})

import altair as alt
alt.Chart(df).mark_bar().encode(
    x = 'groupbyyear(date)',
    y = 'count(value)',
    color = 'value'
)

Upvotes: 1

Views: 718

Answers (1)

jakevdp
jakevdp

Reputation: 86433

You're very close: instead of groupbyyear you can use a year time unit transform, and since your dates are non-standard format, you can first use pandas to_datetime to convert them to standard date values. The result looks like this:

import altair as alt
import pandas as pd

df = pd.DataFrame({
    'date': ['20-03-2017', '20-03-2017', '20-03-2018', '21-03-2018', '20-10-2019', '20-03-2019', '1-02-2019', '10-03-2020', '20-06-2020'],
    'value': [True, True, True, False, True, False, False, True, False]
})

df['date'] = pd.to_datetime(df['date'])

alt.Chart(df).mark_bar().encode(
    x = 'year(date):O',
    y = 'count(value)',
    color = 'value'
)

enter image description here

Upvotes: 1

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