pandas 如何在 matplotlib 中绘制置信区间？
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How to plot confidence interval in matplotlib?
提问by Nate Reed
I'm using matplotlib to plot the distribution of a data set, and want to overlay vertical lines for the confidence interval.
我正在使用 matplotlib 绘制数据集的分布，并希望为置信区间叠加垂直线。
The density plot looks fine, but I don't see the line. Any ideas?
密度图看起来不错，但我没有看到这条线。有任何想法吗？
# Get data
import urllib.request as request
request.urlretrieve('http://seanlahman.com/files/database/baseballdatabank-master_2016-03-02.zip', "baseballdatabank-master_2016-03-02.zip")
from zipfile import ZipFile
zip = ZipFile('baseballdatabank-master_2016-03-02.zip')
zip.extractall()
import pandas as pd
import matplotlib.pyplot as plt
%matplotlib inline
batting_df = pd.read_csv("baseballdatabank-master\core\Batting.csv")
batting_df = batting_df[batting_df['AB'] > 20]
batting_df['batting_average'] = batting_df['H'] / batting_df['AB']
# Plot distribution
batting_averages = batting_df['batting_average'].dropna()
batting_averages.plot.kde()
# Plot confidence interval
import scipy.stats
import numpy as np, scipy.stats as st
stderr = st.sem(batting_averages)
interval1 = (batting_averages.mean() - stderr * 1.96, batting_averages.mean() + stderr * 1.96)
plt.plot(interval1[0], 12)
plt.show()
I'm trying to plot the vertical line at the x coordinate of the first interval, which is centered around the mean. I passed 12 as the y coordinate as this is highest value shown on the y axis.
我试图在第一个区间的 x 坐标处绘制垂直线，该坐标以均值为中心。我通过 12 作为 y 坐标，因为这是 y 轴上显示的最高值。
回答by Luis
If you catch the axes of the kdeplot like this:
如果您kde像这样捕捉绘图的轴：
ax = batting_averages.plot.kde()
... then you can plot vertical lines at any position you want:
...然后你可以在你想要的任何位置绘制垂直线：
stderr = st.sem(batting_averages)
ax.vlines( x=batting_averages.mean(), ymin=-1, ymax=15, color='red', label='mean' )
stderr = 0.1
ax.vlines( x=batting_averages.mean() - stderr * 1.96, ymin=-1, ymax=15, color='green', label='95% CI' )
ax.vlines( x=batting_averages.mean() + stderr * 1.96, ymin=-1, ymax=15, color='green' )
ax.set_ylim([-1,12])
ax.legend()
plt.show()
which gives you the following graph:
它为您提供以下图表：
(note that I changed the standard error to make the lines visible)
（请注意，我更改了标准错误以使线条可见）
回答by Nate Reed
Plot takes two arguments, x and y. In this case, I need to pass the x coordinates of the two points that define the line, followed by the y coordinates of the two points:
Plot 有两个参数，x 和 y。在这种情况下，我需要传递定义线的两个点的 x 坐标，然后是这两个点的 y 坐标：
plot((x1, x2), (y1, y2))
Substituting the variables from the example above:
替换上例中的变量：
plt.plot((interval1[0], interval1[0]), (0, 12))
plt.plot((interval1[1], interval1[1]), (0, 12))
