pandas 类型错误：将第二个图例添加到绘图时，“PathCollection”对象不可迭代
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TypeError: 'PathCollection' object is not iterable when adding second legend to plot
提问by Stefano Potter
I am making a scatter plot from three separate dataframes and plotting the points as well as the best fit lines. I can accomplish this using this code:
我正在从三个单独的数据框中制作散点图，并绘制点以及最佳拟合线。我可以使用以下代码完成此操作：
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
fig=plt.figure()
ax1=fig.add_subplot(111)
ax2=fig.add_subplot(111)
ax3=fig.add_subplot(111)
#create scatter plots from the dataframes
ax1.scatter(ex_x, ex_y, s=10, c='r', label='Fire Exclusion')
ax2.scatter(one_x,one_y, c='b', marker='s',label='One Fire')
ax3.scatter(two_x, two_y, s=10, c='g', marker='^', label='Two Fires')
#plot lines of best fit
ax1.plot(ex_x,ex_results.predict(), color = 'r',label = 'Linear (Fire Exclusion)')
ax2.plot(one_x,one_results.predict(), color = 'b',label = 'Linear (One Fire)')
ax3.plot(two_x,two_results.predict(), color = 'g',label = 'Linear (Two Fires)')
#add legend and axis labels
plt.xlabel('NDVI 2004/07/27')
plt.ylabel('NDVI 2005/07/14')
plt.title('NDVI in 2004 vs. 2005')
plt.legend(loc='center left', bbox_to_anchor=(1, 0.5), scatterpoints=1)
which gives me:
这给了我：
Now I want to add a second legend which will display the r2 for each line. I am attempting to do that like this:
现在我想添加第二个图例，它将显示每行的 r2。我正在尝试这样做：
fig=plt.figure()
ax1=fig.add_subplot(111)
ax2=fig.add_subplot(111)
ax3=fig.add_subplot(111)
scat1,=ax1.scatter(ex_x, ex_y, s=10, c='r', label='Fire Exclusion')
scat2,=ax2.scatter(one_x,one_y, c='b', marker='s',label='One Fire')
scat3,=ax3.scatter(two_x, two_y, s=10, c='g', marker='^', label='Two Fires')
lin1,=ax1.plot(ex_x,ex_results.predict(), color = 'r',label = 'Linear (Fire Exclusion)')
lin2,=ax2.plot(one_x,one_results.predict(), color = 'b',label = 'Linear (One Fire)')
lin3,=ax3.plot(two_x,two_results.predict(), color = 'g',label = 'Linear (Two Fires)')
l1 = plt.legend([scat1, scat2,scat3,lin1,lin2,lin3], ["Fire Exclusion", "One Fire", "Two Fires", "Linear (Fire Exclusion)", "Linear (One Fire)", "Linear (Two Fires)"], loc='upper left', scatterpoints=1)
#get r2 from regression results
r2ex=ex_results.rsquared
r2one=one_results.rsquared
r2two=two_results.rsquared
plt.legend([r2ex, r2one, r2two], ['R2 (Fire Exclusion)', 'R2 (One Fire)', 'R2 (Two Fires)'], loc='lower right')
plt.gca().add_artist(l1)
plt.xlabel('NDVI 2004/07/27')
plt.ylabel('NDVI 2005/07/14')
plt.title('NDVI in 2004 vs. 2005')
but this returns:
但这会返回：
Traceback (most recent call last):
File "<ipython-input-32-b6277bf27ded>", line 1, in <module>
runfile('E:/prelim_codes/Fire.py', wdir='E:/prelim_codes')
File "C:\Users\Stefano\Anaconda2_2\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 714, in runfile
execfile(filename, namespace)
File "C:\Users\Stefano\Anaconda2_2\lib\site-packages\spyderlib\widgets\externalshell\sitecustomize.py", line 74, in execfile
exec(compile(scripttext, filename, 'exec'), glob, loc)
File "E:/prelim_codes/Fire.py", line 539, in <module>
scat1,=ax1.scatter(ex_x, ex_y, s=10, c='r', label='Fire Exclusion')
TypeError: 'PathCollection' object is not iterable
回答by j sad
I had the same error. I found out that you shouldn't include the comma after your variable names. So try
我有同样的错误。我发现您不应该在变量名后包含逗号。所以试试
scat1 =ax1.scatter(ex_x, ex_y, s=10, c='r', label='Fire Exclusion')
scat2 =ax2.scatter(one_x,one_y, c='b', marker='s',label='One Fire')
scat3 =ax3.scatter(two_x, two_y, s=10, c='g', marker='^', label='Two Fires')
instead of
代替
scat1,=ax1.scatter(ex_x, ex_y, s=10, c='r', label='Fire Exclusion')
scat2,=ax2.scatter(one_x,one_y, c='b', marker='s',label='One Fire')
scat3,=ax3.scatter(two_x, two_y, s=10, c='g', marker='^', label='Two Fires')
This is because axes.scatterreturns a PathCollection unlike axes.plot which returns a tuple of the lines plotted (see http://matplotlib.org/1.3.1/users/pyplot_tutorial.html#controlling-line-propertiesand Python code. Is it comma operator?).
这是因为axes.scatter返回一个PathCollection，与axes.plot 不同，后者返回绘制的线的元组（参见http://matplotlib.org/1.3.1/users/pyplot_tutorial.html#controlling-line-properties和Python 代码。是逗号运算符吗？）。
So for your lines you will still need the comma because you are unpacking the tuple but for the scatter you should not have the comma.
因此，对于您的行，您仍然需要逗号，因为您正在解包元组，但对于散点图，您不应该使用逗号。
