Python 了解 Pandas 散点矩阵图中的对角线
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Understanding the diagonal in Pandas' scatter matrix plot
提问by Hyman Twain
I'm plotting a scatter plot with Pandas. I can understand the plot, except the curves in diagonal plots. Can someone explain to me what they mean?
我正在绘制散点图Pandas。除了对角线图中的曲线，我能理解这个图。有人可以向我解释他们的意思吗？
Image:
图片：
Code:
代码：
import pylab
import numpy as np
from pandas.tools.plotting import scatter_matrix
import pandas as pd
def make_scatter_plot(X, name):
"""
Make scatterplot.
Parameters:
-----------
X:a design matrix where each column is a feature and each row is an observation.
name: the name of the plot.
"""
pylab.clf()
df = pd.DataFrame(X)
axs = scatter_matrix(df, alpha=0.2, diagonal='kde')
for ax in axs[:,0]: # the left boundary
ax.grid('off', axis='both')
ax.set_yticks([0, .5])
for ax in axs[-1,:]: # the lower boundary
ax.grid('off', axis='both')
ax.set_xticks([0, .5])
pylab.savefig(name + ".png")
回答by Wilduck
As you can tell, the scatter matrix is plotting each of the columns specified against each other column.
如您所知，散点矩阵将指定的每一列相对于其他列进行绘制。
However, in this format, when you got to a diagonal, you would see a plot of a column against itself. Since this would always be a straight line, Pandas decides it can give you more useful information, and plots the density plot of just that column of data.
但是，在这种格式中，当您到达对角线时，您会看到一个柱状图。由于这始终是一条直线，Pandas 认为它可以为您提供更多有用的信息，并绘制仅该列数据的密度图。
See http://pandas.pydata.org/pandas-docs/stable/visualization.html#density-plot.
请参阅http://pandas.pydata.org/pandas-docs/stable/visualization.html#density-plot。
If you would rather have a histogram, you could change your plotting code to:
如果您更喜欢直方图，您可以将绘图代码更改为：
axs = scatter_matrix(df, alpha=0.2, diagonal='hist')
回答by scarybuh
Plotting methods allow for a handful of plot styles other than the default Line plot. These methods can be provided as the kind keyword argument to plot(). These include:
绘图方法允许使用除默认线图之外的少数绘图样式。这些方法可以作为 plot() 的 kind 关键字参数提供。这些包括：
- ‘bar' or ‘barh' for bar plots
- ‘hist' for histogram
- ‘box' for boxplot
- ‘kde' or 'density' for density plots
- ‘area' for area plots
- ‘scatter' for scatter plots
- ‘hexbin' for hexagonal bin plots
- ‘pie' for pie plots
- 'bar' 或 'barh' 用于条形图
- 'hist' 用于直方图
- 箱线图的“箱”
- 密度图的“kde”或“密度”
- 'area' 用于面积图
- 散点图的 'scatter'
- 'hexbin' 用于六边形 bin 图
- 'pie' 表示饼图
https://pandas.pydata.org/pandas-docs/stable/visualization.html
https://pandas.pydata.org/pandas-docs/stable/visualization.html
