Here is my data frame:

I would like to plot a chart like this:

How would I do this in altair charts in python?

CodePudding user response：

You can just do

df.set_index(['student','subject']).plot.bar(rot=0)

CodePudding user response：

In the development version of Altair (installable from GitHub), you can use the new xOffset property to recreate the chart you want:

import pandas as pd
import altair as alt


df = pd.DataFrame({
    'student': ['A', 'A', 'B', 'B', 'C', 'C'],
    'subject': ['Math', 'English', 'Math', 'English', 'Math', 'English'],
    'current': [98, 88, 68, 72, 92, 92],
    'previous': [92, 94, 71, 71, 88, 84],
}).melt(
    id_vars=['student', 'subject'],
    var_name='score_type',
    value_name='score'
)


alt.Chart(df).mark_bar().encode(
    x=alt.X('subject', title='', axis=alt.Axis(labelAngle=0)),
    xOffset='score_type',
    color=alt.Color('score_type', legend=alt.Legend(orient='bottom', title='')),
    y='score',
    column=alt.Column('student', header=alt.Header(orient='bottom', title=''))
)

Btw, try to post you data as text instead of a screenshot and it will be quicker for someone to help out since they can copy and paste it.