如何使 matplotlib 中条形图的 xticks 居中？

Question

我按照本教程在我的条形图中添加值 link

博客中的代码是这样写的

from matplotlib import pyplot as plt
import numpy as np

years = [1901, 1911, 1921, 1931, 1941, 1951, 1961, 1971, 1981, 1991, 2001, 2011]
population = [237.4, 238.4, 252.09, 251.31, 278.98, 318.66, 361.09, 439.23, 548.16, 683.33, 846.42, 1028.74]

x = np.arange(len(years)) # the label locations
width = 0.35 # the width of the bars

fig, ax = plt.subplots()

ax.set_ylabel('Population(in million)')
ax.set_title('Years')
ax.set_xticks(x)
ax.set_xticklabels(years)

pps = ax.bar(x - width/2, population, width, label='population')
for p in pps:
   height = p.get_height()
   ax.annotate('{}'.format(height),
      xy=(p.get_x() + p.get_width() / 2, height),
      xytext=(0, 3), # 3 points vertical offset
      textcoords="offset points",
      ha='center', va='bottom')

plt.show()

所以，输出变成这样

但是，我刚刚发现条形图中的 xticks 没有居中

我的问题 - 有人知道如何使 xticks 居中吗？

我试图找到解决方案，但尚未找到

任何帮助将不胜感激，谢谢

Answer 1

imo 该教程使绘图变得比需要的更加混乱。您很少需要从绘图中的艺术家那里获取坐标。直接使用您的数据即可：

from matplotlib import pyplot as plt
import numpy as np

years = [1901, 1911, 1921, 1931, 1941, 1951, 1961, 1971, 1981, 1991, 2001, 2011]
population = [237.4, 238.4, 252.09, 251.31, 278.98, 318.66, 361.09, 439.23, 548.16, 683.33, 846.42, 1028.74]

x_values = np.arange(len(years))
fig, ax = plt.subplots(figsize=(12, 4))

ax.bar(x_values, population, width=.35, label='population')
for x, y in zip(x_values, population):    
    ax.annotate(
        str(y),        # label is our y-value as a string
        xy=(x, y),
        xytext=(0, 3), # 3 points vertical offset
        textcoords="offset points",
        ha='center', 
        va='bottom'
    )
    
    
ax.set_xticks(x_values)
ax.set_xticklabels(years)
ax.set_ylim(0, 1200)

plt.show()

Answer 2

在 matplotlib 3.4.0 或更高版本中 bar_label can be used instead of annotate:

import numpy as np
from matplotlib import pyplot as plt

years = [1901, 1911, 1921, 1931, 1941, 1951, 1961, 1971, 1981, 1991, 2001, 2011]
population = [237.4, 238.4, 252.09, 251.31, 278.98, 318.66, 361.09, 439.23,
              548.16, 683.33, 846.42, 1028.74]

# Create Tick Locations
x = np.arange(len(years))
# Plotting
fig, ax = plt.subplots(figsize=(10, 6))
# Do not offset the values of x to center labels (default)
ax.bar(x, population, width=.35, label='population')

# Labels, ticks, etc.
ax.set_ylabel('Population(in million)')
ax.set_title('Years')
ax.set_xticks(x)
ax.set_xticklabels(years)

# Add Bar Labels
for c in ax.containers:
    ax.bar_label(c)

plt.show()

如何使 matplotlib 中条形图的 xticks 居中？

How to center the xticks from a bar chart in matplotlib?

python

numpy

matplotlib

bar-chart

xticks