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Altair中的空散点图

altair pandas python

Jsevillamol · 技术社区 · 4 年前

我很困惑为什么这个代码不起作用:

#@title Visualize trends in accelerators

x_axis = 'Release Year'
y_axis = 'FP32 (single precision) Performance [FLOP/s]'

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

# Download data
key = '1AAIebjNsnJj_uKALHbXNfn3_YsT6sHXtCU0q7OIPuc4'
sheet_name = 'HARDWARE_DATA'
url = f'https://docs.google.com/spreadsheets/d/{key}/gviz/tq?tqx=out:csv&sheet={sheet_name}'
df = pd.read_csv(url)

# Filter NaN datapoints
df = df[~df[x_axis].isna()]
df = df[~df[y_axis].isna()]

# Plot the dataset
alt.themes.enable('fivethirtyeight')
alt.Chart(df).mark_circle(size=60).encode(
  x=alt.X(f'{x_axis}:Q',
          scale=alt.Scale(
                          domain=(df[x_axis].min(), df[x_axis].max())
                          ),
          axis=alt.Axis(format=".0f")
          ),
  y=alt.Y(f'{y_axis}:Q',
          scale=alt.Scale(
                          domain=(df[y_axis].min(), df[y_axis].max())
                          ),
          axis=alt.Axis(format=".1e")
          ),
)

当我用seaborn绘制它时,它就起作用了

import seaborn as sns
sns.set_theme()
sns.regplot(x=df[x_axis], y=df[y_axis]);

没有显示任何错误消息,只有空的绘图。控制台发出此警告

DevTools failed to load source map: Could not load content for https://cdn.jsdelivr.net/npm/vega-embed.min.js.map: HTTP error: status code 404, net::ERR_HTTP_RESPONSE_CODE_FAILURE

发生了什么事?

0 回复 | 直到 4 年前

jakevdp 4 年前

问题是您的列名中有特殊字符,需要在Altair中转义(例如,请参阅 field 中的文档 https://altair-viz.github.io/user_guide/generated/core/altair.Color.html?highlight=escape )

为什么会这样?像这样的字符 . 和 [] Vega-Lite中用于访问列的嵌套属性。

最简单的方法是避免在数据帧列名中使用此类特殊字符。或者,您可以用反斜杠转义特殊字符( \ )不过要小心Python字符串中反斜杠的效果(使用 r 用于原始字符串编码的前缀)。例如

x_axis = 'Release Year'
y_axis = 'FP32 (single precision) Performance [FLOP/s]'
y_axis_escaped = r'FP32 (single precision) Performance \[FLOP/s\]'

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

# Download data
key = '1AAIebjNsnJj_uKALHbXNfn3_YsT6sHXtCU0q7OIPuc4'
sheet_name = 'HARDWARE_DATA'
url = f'https://docs.google.com/spreadsheets/d/{key}/gviz/tq?tqx=out:csv&sheet={sheet_name}'
df = pd.read_csv(url)

# Filter NaN datapoints
df = df[~df[x_axis].isna()]
df = df[~df[y_axis].isna()]

# Plot the dataset
alt.themes.enable('fivethirtyeight')
alt.Chart(df).mark_circle(size=60).encode(
  x=alt.X(f'{x_axis}:Q',
          scale=alt.Scale(
                          domain=(df[x_axis].min(), df[x_axis].max())
                          ),
          axis=alt.Axis(format=".0f")
          ),
  y=alt.Y(f'{y_axis_escaped}:Q',
          scale=alt.Scale(
                          domain=(df[y_axis].min(), df[y_axis].max())
                          ),
          axis=alt.Axis(format=".1e")
          ),
)