用pandas和matplotlib绘制 [英] Plotting with pandas and matplotlib

问题描述

我正在尝试在Python中创建散点图.我有一个具有指定类别的数据框'df'，x和y是列号:

I'm trying to create a scatter plot in Python. I have a dataframe 'df' with a specified category and x and y are column numbers:

groups = df.groupby(category)
fig, ax = plt.subplots()
for name, group in groups:
    ax.plot(x=group.iloc[:,x], y=group.iloc[:,y], marker='o', linestyle='',label=name)
fig = ax.get_figure()
fig.savefig(path)

由于某种原因，我得到了一个空的散点图-我做错什么了吗?

For some reason, I am getting an empty scatterplot -- Am I doing something wrong?

推荐答案

ax.plot 没有x和y自变量.

签名为Axes.plot(*args, **kwargs)，这意味着x和y只是位置参数.如果指定x=和y=，它们将被视为关键字参数并被忽略.

The signature is Axes.plot(*args, **kwargs), meaning that x and y are simply positional arguments. If you specify x= and y= they will be treated as keyword arguments and ignored.

因此从代码中删除x=和y=

ax.plot(group.iloc[:,x], group.iloc[:,y], marker='o', linestyle='',label=name)

完整示例:

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame({"x":np.random.rand(40), 
                   "y":np.random.rand(40),
                   "category": np.random.choice(list("ABCD"), size=40)})
category = "category"
x=1; y=2
groups = df.groupby(category)
fig, ax = plt.subplots()
for name, group in groups:
    ax.plot(group.iloc[:,x], group.iloc[:,y], marker='o', linestyle='',label=name)
fig = ax.get_figure()
#fig.savefig(path)
plt.show()

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