如何使用pyplot.bar绘制正误差条？

Question

我正在尝试用正误差线和图中的最大值绘制4个平均值。

means   = [26.82,26.4,61.17,61.55]         # Mean Data 
stds    = [4.59,4.39,4.37,4.38]            # Standard deviation Data
peakval = ['26.82','26.4','61.17','61.55'] # String array of means

ind = np.arange(len(means))
width = 0.35
colours = ['red','blue','green','yellow']

pyplot.figure()
pyplot.title('Average Age')
for i in range(len(means)):
    pyplot.bar(ind[i],means[i],width,color=colours[i],align='center',yerr=stds[i],ecolor='k')
pyplot.ylabel('Age (years)')
pyplot.xticks(ind,('Young Male','Young Female','Elderly Male','Elderly Female'))

def autolabel(bars,peakval):
    for ii,bar in enumerate(bars):
        height = bars[ii]
        pyplot.text(ind[ii], height-5, '%s'% (peakval[ii]), ha='center', va='bottom')
autolabel(means,peakval)    

但是我无法找出如何只绘制正误差条。 所以我最终得到了这样的图表：

任何建议都将不胜感激。

Answer 1

如果我理解正确，你可以这样做：

import numpy as np
from matplotlib import pyplot

means   = [26.82,26.4,61.17,61.55]           # Mean Data 
stds    = [(0,0,0,0), [4.59,4.39,4.37,4.38]] # Standard deviation Data
peakval = ['26.82','26.4','61.17','61.55']   # String array of means

ind = np.arange(len(means))
width = 0.35
colours = ['red','blue','green','yellow']

pyplot.figure()
pyplot.title('Average Age')
pyplot.bar(ind, means, width, color=colours, align='center', yerr=stds, ecolor='k')
pyplot.ylabel('Age (years)')
pyplot.xticks(ind,('Young Male','Young Female','Elderly Male','Elderly Female'))

def autolabel(bars,peakval):
    for ii,bar in enumerate(bars):
        height = bars[ii]
        pyplot.text(ind[ii], height-5, '%s'% (peakval[ii]), ha='center', va='bottom')
autolabel(means,peakval) 
pyplot.show()

结果：

这样做是因为您可以传递yerr一个2xN列表，代表正面和负面的“抵消”，请参阅documentation。