条的宽度相同!它们看起来不一样的原因是因为您正在使用以下行:
index = np.arange(n_groups)
这将更改您的x值,从而更改x轴的比例。为了抵消这种影响,您可以更改x轴的限制,也可以使条形宽度取决于分数的数量,例如,如果0.35的宽度适用于10个分数,那么如果将分数的数量加倍,条宽度的一半(反之亦然)。您可以看到更改轴限制或条宽度如何使条看起来相同的宽度:
import numpy as np
import matplotlib.pyplot as plt
# make some dummy data
scores_reading = np.random.randint(50,100,10)
scores_math = np.random.randint(50,100,10)
fig = plt.figure(figsize=(16,5))
bar_width = 0.35
index = np.arange(10)
ax1 = fig.add_subplot(1,4,1)
ax1.bar(index, scores_reading, bar_width, fc='b', edgecolor='none')
ax1.bar(index+bar_width, scores_math, bar_width, fc='r', edgecolor='none')
ax1.set_xlim(0,10)
ax1.set_title('Original - 10 scores')
ax2 = fig.add_subplot(1,4,2)
ax2.bar(index[:5], scores_reading[:5], bar_width, fc='b', edgecolor='none')
ax2.bar(index[:5]+bar_width, scores_math[:5], bar_width, fc='r', edgecolor='none')
ax2.set_title('Original - 5 scores')
ax3 = fig.add_subplot(1,4,3)
ax3.bar(index[:5], scores_reading[:5], bar_width, fc='b', edgecolor='none')
ax3.bar(index[:5]+bar_width, scores_math[:5], bar_width, fc='r', edgecolor='none')
ax3.set_xlim(0,10)
ax3.set_title('Changed limit - 5 scores')
ax4 = fig.add_subplot(1,4,4)
ax4.bar(index[:5], scores_reading[:5], bar_width/2., fc='b', edgecolor='none')
ax4.bar(index[:5]+bar_width, scores_math[:5], bar_width/2., fc='r', edgecolor='none')
ax4.set_title('Changed width - 5 scores')
fig.show()