如何在这个 matplotlib 图中修复条形宽度

Question

有人可以告诉我如何修改这个使用 matplotlib 的 Python 代码，这样无论绘制多少分数，条形的宽度都将保持不变？提前谢谢！

# data to plot
  n_groups = len(math_scores)
  ###print "im here", math_scores,verbal_scores
  scores_readingwriting = verbal_scores
  scores_math = math_scores

# create plot
  fig, ax = plot.subplots()
  index = np.arange(n_groups)
  bar_width = 0.35
  opacity = 0.8

  rects1 = plot.bar(index, scores_readingwriting, bar_width,
                 alpha=opacity,
                 color='black',
                 label='R/W')

  rects2 = plot.bar(index + bar_width, scores_math, bar_width,
                 alpha=opacity,
                 color='grey',
                 label='Math')

  plot.xlabel('Date',size='14')
  plot.ylabel('Scores',size='14')

  plot.title(str(first_names[i])+' '+str(last_names[i])+"'s History",size='17')
  num=len(scores)
  ###print datesofinterest
  plot.xticks(index + bar_width/2, datesofinterest,size='12')
  plot.yticks(size='12')
  axes = plot.gca()
  axes.set_ylim([200,800])
  plot.legend()

  plot.tight_layout()
  fig.savefig('img'+str(student_ids[i])+'.png')

Answer 1

条的宽度相同！它们看起来不一样的原因是因为您使用的是这一行：

index = np.arange(n_groups)

这将改变你的 x 值，从而改变你的 x 轴的比例。为了抵消这种影响，您可以更改 x 轴的限制，或者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，那么如果您将分数加倍，您将条宽度的一半（反之亦然）。您可以看到更改轴限制或条形宽度如何使条形看起来相同宽度：

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()