Altair:没有排序轴

Question

这是一些简单的示例代码,演示了我想要解决的问题:

import pandas as pd
import altair as alt

categoryNames    = [ 'a', 'f', 'r', 'u', 'p' ]
categories       = pd.Series( categoryNames )
categories.index = categoryNames

amountsRaw       = [ 50, -100, 75, 100, -500 ]
amounts          = pd.Series( amountsRaw )
amounts.index    = categoryNames

df = pd.DataFrame( { "Amounts" : amounts, "Categories" : categories } )

alt.Chart( df ).mark_bar().encode(
    x='Categories',
    y='Amounts',
    color = alt.condition( alt.datum.Amounts > 0, alt.value( 'green' ), alt.value( 'red' ) )
)

这将生成一个条形图,但我不希望对x轴类别进行排序.它们需要以与在categoryNames数组中相同的顺序出现.我怎样才能做到这一点？

Answer 1

您可以将列表传递给编码的sort属性alt.X以控制类别的顺序.例如:

alt.Chart(df).mark_bar().encode(
    x=alt.X('Categories', sort=categoryNames),
    y='Amounts',
    color=alt.condition(alt.datum.Amounts > 0, alt.value('green'), alt.value('red'))
)