Pandas：在同一个图上绘制两个直方图
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Pandas: plotting two histograms on the same plot
提问by meto
I would like to have 2 histograms to appear on the same plot (with different colors, and possibly differente alphas). I tried
我希望有 2 个直方图出现在同一个图上（具有不同的颜色，并且可能具有不同的 alpha）。我试过
import random
x = pd.DataFrame([random.gauss(3,1) for _ in range(400)])
y = pd.DataFrame([random.gauss(4,2) for _ in range(400)])
x.hist( alpha=0.5, label='x')
y.hist(alpha=0.5, label='y')
x.plot(kind='kde', style='k--')
y.plot(kind='kde', style='k--')
plt.legend(loc='upper right')
plt.show()
This produces the result in 4 different plots. How can I have them on the same one?
这会在 4 个不同的图中产生结果。我怎么能把它们放在同一个上面？
回答by rustil
If I understood correctly, both hists should go into the same subplot. So it should be
如果我理解正确，两个历史应该进入同一个子图。所以应该是
fig = plt.figure()
ax = fig.add_subplot(111)
_ = ax.hist(x.values)
_ = ax.hist(y.values, color='red', alpha=.3)
You can also pass the pandas plot method an axis object, so if you want both kde's in another plot do:
您还可以将 pandas 绘图方法传递给轴对象，因此如果您希望在另一个绘图中同时使用两个 kde，请执行以下操作：
fig = plt.figure()
ax = fig.add_subplot(111)
x.plot(kind='kde', ax=ax)
y.plot(kind='kde', ax=ax, color='red')
To get everything into a single plot you need two different y-scales since kde is density and histogram is frequency. For that you use the axes.twinx()command.
要将所有内容整合到一个图中，您需要两个不同的 y 尺度，因为 kde 是密度，直方图是频率。为此，您使用axes.twinx()命令。
fig = plt.figure()
ax = fig.add_subplot(111)
_ = ax.hist(x.values)
_ = ax.hist(y.values, color='red', alpha=.3)
ax1 = ax.twinx()
x.plot(kind='kde', ax=ax1)
y.plot(kind='kde', ax=ax1, color='red')
回答by polku
You can use plt.figure() and the function add_subplot(): the first 2 arguments are the number of rows and cols you want in your plot, the last is the position of the subplot in the plot.
您可以使用 plt.figure() 和函数 add_subplot()：前 2 个参数是绘图中所需的行数和列数，最后一个是绘图中子图的位置。
fig = plt.figure()
subplot = fig.add_subplot(1, 2, 1)
subplot.hist(x.ix[:,0], alpha=0.5)
subplot = fig.add_subplot(1, 2, 2)
subplot.hist(y.ix[:,0], alpha=0.5)
