向 Altair 图形添加背景实心填充

Question

我非常喜欢 Altair 用 Python 制作图表。作为致敬，我想在"Mistakes, we’ve drawn a few" 中重新生成经济学人图表： 这是第一枪的代码：

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

 df = pd.read_csv('http://infographics.economist.com/databank/Economist_corbyn.csv').dropna()

 bars = alt.Chart(df, title="Average number of likes per Facebook post").mark_bar().
    encode(
        y=alt.Y('Page:O', axis=alt.Axis(title=''),
        sort=alt.EncodingSortField(
           field="Average number of likes per Facebook post 2016:Q",  # The field to use for the sort
           op="sum",  # The operation to run on the field prior to sorting
           order="ascending"  # The order to sort in
       )),
       color=alt.value("#116EA1"),
       x=alt.X("Average number of likes per Facebook post 2016:Q", 
       axis=alt.Axis(title='Average number of likes per Facebook post')),
)


text = bars.mark_text(
    align='left',
    baseline='middle',
    dx=3,  # Nudges text to right so it doesn't appear on top of the bar,
).encode(
    text='Average number of likes per Facebook post 2016:Q'
)

(bars+text).configure_title(fontSize=14)

四个问题：

1. 如何用纯色##D9E9F0 填充背景？

2. 如何使第一行弹出（通过在粗体标签上添加框 “杰里米·科尔宾”）？

3. 我可以在左下角添加浅灰色的版权声明吗 版本 3 中新的 Altair 文本层可能性的角落？ 如果是这样，该怎么做？

4. 如何将 xticks 放在图表顶部？

感谢您的帮助！

更新来自jakevdp 和aberna 的 (1) 和 (4) 答案：

df['x'] = df['Average number of likes per Facebook post 2016']/1000.0
bars = alt.Chart(
    df, title="Average number of likes per Facebook post ('000)"
).mark_bar().encode(
    y=alt.Y('Page:O', axis=alt.Axis(title=''),
           sort=alt.EncodingSortField(
            field="Average number of likes per Facebook post 2016:Q",  # The field to use for the sort
            op="sum",  # The operation to run on the field prior to sorting
            order="ascending"  # The order to sort in
        )),
    color=alt.value("#116EA1"),
    x=alt.X("x:Q", 
            axis=alt.Axis(title='', orient="top"),
            scale=alt.Scale(round=True, domain=[0,5])),
)

bars.configure_title(fontSize=14).configure(background='#D9E9F0')

Answer 1

回答您的一个问题：您可以使用configure(background="colorname") 添加背景。例如：

(bars+text).configure_title(fontSize=14).configure(background='#DDEEFF')

Answer 2

回答您的问题 4，您需要在 alt.Axis 中使用 orient="top" 参数。

axis=alt.Axis(title='Average number of likes per Facebook post',orient="top"))

Answer 3

有点回答问题 2。不是突出显示栏，而是通过条件字体样式突出显示标签。

label_style = {
    "condition": [{"test" : "datum.value == 'Jeremy Corbyn'", "value": "bold"}],
    "value": "italic"
}

...

y=alt.Y("Page:N", axis=alt.Axis(title="", labelFontStyle=label_style))