使用 Emoji 的象形图可视化

象形图可视化显示了动物在英国和美国的分布，使用 Unicode Emoji 标记而非自定义 SVG 路径（参见 https://vega-altair.cn/gallery/isotype.html）。这改编自 Vega-Lite 示例 https://vega.github.io/vega-lite/examples/isotype_bar_chart_emoji.html。

方法语法

import altair as alt
import pandas as pd

source = pd.DataFrame([
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'pigs'},
      {'country': 'Great Britain', 'animal': 'pigs'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'}
    ])


alt.Chart(source).mark_text(size=45, baseline='middle').encode(
    alt.X('x:O').axis(None),
    alt.Y('animal:O').axis(None),
    alt.Row('country:N').title(''),
    alt.Text('emoji:N')
).transform_calculate(
    emoji="{'cattle': '🐄', 'pigs': '🐖', 'sheep': '🐏'}[datum.animal]"
).transform_window(
    x='rank()',
    groupby=['country', 'animal']
).properties(
    width=550,
    height=140
)

属性语法

import altair as alt
import pandas as pd

source = pd.DataFrame([
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'cattle'},
      {'country': 'Great Britain', 'animal': 'pigs'},
      {'country': 'Great Britain', 'animal': 'pigs'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'Great Britain', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'cattle'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'pigs'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'},
      {'country': 'United States', 'animal': 'sheep'}
    ])


alt.Chart(source).mark_text(size=45, baseline='middle').encode(
    alt.X('x:O', axis=None),
    alt.Y('animal:O', axis=None),
    alt.Row('country:N', header=alt.Header(title='')),
    alt.Text('emoji:N')
).transform_calculate(
    emoji="{'cattle': '🐄', 'pigs': '🐖', 'sheep': '🐏'}[datum.animal]"
).transform_window(
    x='rank()',
    groupby=['country', 'animal']
).properties(width=550, height=140)