带有水平连接图表的两个标题

Question

我想连接两个图表，然后美化生成的组合图表（添加一些漂亮的背景）。这里的一件重要事情是尝试保留两个图表的标题。

当我尝试这样做时，我要么得到只有一个标题的美化组合图表，要么出现错误：ValueError: Objects with "background" attribute cannot be used within HConcatChart. Consider defining the background attribute in the HConcatChart object instead.

这是我尝试过的一些虚拟代码片段。

尝试 #1，它只产生一个标题：

import altair as alt
from vega_datasets import data

source = data.cars()

line = alt.Chart(source).mark_line().encode(
    x='Year',
    y='mean(Miles_per_Gallon)'
)

band = alt.Chart(source).mark_errorband(extent='ci').encode(
    x='Year',
    y=alt.Y('Miles_per_Gallon', title='Miles/Gallon'),
)

combined = band | line
combined
combined.properties(background = '#f9f9f9',
                    title = alt.TitleParams(text = 'General title', 
                                            subtitle = ['Subtitle'],
                                            font = 'Ubuntu Mono', 
                                            fontSize = 22, 
                                            color = '#3E454F', 
                                            subtitleFont = 'Ubuntu Mono',
                                            subtitleFontSize = 16, 
                                            subtitleColor = '#3E454F')
                  )

尝试#2 产生值错误：

line2 = line.properties(background = '#f9f9f9',
                    title = alt.TitleParams(text = 'General title 1', 
                                            subtitle = ['Subtitle'],
                                            font = 'Ubuntu Mono', 
                                            fontSize = 22, 
                                            color = '#3E454F', 
                                            subtitleFont = 'Ubuntu Mono',
                                            subtitleFontSize = 16, 
                                            subtitleColor = '#3E454F')
                  )

band2 = band.properties(background = '#f9f9f9',
                    title = alt.TitleParams(text = 'General title 2', 
                                            subtitle = ['Subtitle'],
                                            font = 'Ubuntu Mono', 
                                            fontSize = 22, 
                                            color = '#3E454F', 
                                            subtitleFont = 'Ubuntu Mono',
                                            subtitleFontSize = 16, 
                                            subtitleColor = '#3E454F')
                  )
line2 | band2

有没有办法实现我想要的？或者 Altair 还不允许这样做？

Answer 1

您可以在单个图表上指定标题，在组合图表上指定背景：

line2 = line.properties(
                    title = alt.TitleParams(text = 'General title 1', 
                                            subtitle = ['Subtitle'],
                                            font = 'Ubuntu Mono', 
                                            fontSize = 22, 
                                            color = '#3E454F', 
                                            subtitleFont = 'Ubuntu Mono',
                                            subtitleFontSize = 16, 
                                            subtitleColor = '#3E454F')
                  )

band2 = band.properties(
                    title = alt.TitleParams(text = 'General title 2', 
                                            subtitle = ['Subtitle'],
                                            font = 'Ubuntu Mono', 
                                            fontSize = 22, 
                                            color = '#3E454F', 
                                            subtitleFont = 'Ubuntu Mono',
                                            subtitleFontSize = 16, 
                                            subtitleColor = '#3E454F')
                  )

combined = band2 | line2
combined.properties(background = '#f9f9f9')

带有水平连接图表的两个标题

Two titles with horizontally concatenated charts

altair