python - Altair:按功能中指定的值旋转文本

Question

我想根据 pandas DataFrame 的列中指定的值旋转文本。看来 text_config 的 angle 参数只接受浮点值，没有特征名称。

import pandas as pd
import altair as alt

data = pd.DataFrame(
    {
        "x": [0, 1, 0, -1],
        "y": [1, 0, -1, 0],
        "name": ["UP", "RIGHT", "BOTTOM", "LEFT"],
        "angle": {180, 270, 0, 90},
    }
)

alt.Chart(data).encode(x="x", y="y", text="name").mark_text(angle='angle')

Answer 1

不幸的是，文本角度不能用作编码 channel 。您能做的最好的事情就是以所需的角度手动分割数据和图层标记；例如:

import pandas as pd
import altair as alt

data = pd.DataFrame(
    {
        "x": [0, 1, 0, -1],
        "y": [1, 0, -1, 0],
        "name": ["UP", "RIGHT", "BOTTOM", "LEFT"],
        "angle": [180, 270, 0, 90],
    }
)

base = alt.Chart(data).encode(x="x", y="y", text="name")

layers = [
    base.transform_filter(alt.datum.name == name).mark_text(angle=angle)
    for (name, angle) in zip(data.name, data.angle)
]

alt.layer(*layers)