Matplotlib: 堆积柱形图的画法

两层堆积

import numpy as np 
import matplotlib.pyplot as plt
 
y1 = np.array([1,2,3,4])
y2 = np.array([1,1,1,1])
x = np.array([2009,2010,2011,2012])
 
plt.figure(figsize=(4,4))
plt.bar(x, y1, label='a')
plt.bar(x, y2, bottom=y1, label='b') 

leg = plt.legend(loc='lower center',frameon=False,bbox_to_anchor=(0.5, -0.18),ncol=2)
plt.show()

效果

多层堆积

关键点在于在画yi时，要计算出yi之前所有数据的和作为bottom，例如：
y3的bottom为y1+y2
y4的bottom为y1+y2+y3

import numpy as np
import matplotlib.pyplot as plt
 
y1 = np.array([1,2,3,4])
y2 = np.array([1,1,1,1])
y3 = np.array([2,1,2,3])
y = [y1, y2, y3]

y_c = np.cumsum(y, 0)
labels = ['a', 'b', 'c']

x = np.array([2009,2010,2011,2012])
 
plt.figure(figsize=(4,4.5))
for i in range(3):
    if i == 0:
        plt.bar(x, y[i], label=labels[i])
    else:
        plt.bar(x, y[i], bottom=y_c[i-1], label=labels[i]) 

leg = plt.legend(loc='lower center',frameon=False,bbox_to_anchor=(0.5, -0.18),ncol=3)

plt.show()

效果