如何绘制和注释分组的条形图

debugcn 发表于 Dev

Prospero

我遇到了一个关于Python中的matplotlib的棘手问题。我想用几个代码创建一个分组的条形图，但是该图表出错。你能给我一些建议吗？代码如下。

import numpy as np
import pandas as pd
file="https://s3-api.us-geo.objectstorage.softlayer.net/cf-courses-data/CognitiveClass/DV0101EN/labs/coursera/Topic_Survey_Assignment.csv"
df=pd.read_csv(file,index_col=0)

df.sort_values(by=['Very interested'], axis=0,ascending=False,inplace=True)

df['Very interested']=df['Very interested']/2233
df['Somewhat interested']=df['Somewhat interested']/2233
df['Not interested']=df['Not interested']/2233
df

df_chart=df.round(2)
df_chart

labels=['Data Analysis/Statistics','Machine Learning','Data Visualization',
       'Big Data (Spark/Hadoop)','Deep Learning','Data Journalism']
very_interested=df_chart['Very interested']
somewhat_interested=df_chart['Somewhat interested']
not_interested=df_chart['Not interested']

x=np.arange(len(labels))
w=0.8

fig,ax=plt.subplots(figsize=(20,8))
rects1=ax.bar(x-w,very_interested,w,label='Very interested',color='#5cb85c')
rects2=ax.bar(x,somewhat_interested,w,label='Somewhat interested',color='#5bc0de')
rects3=ax.bar(x+w,not_interested,w,label='Not interested',color='#d9534f')

ax.set_ylabel('Percentage',fontsize=14)
ax.set_title("The percentage of the respondents' interest in the different data science Area",
            fontsize=16)
ax.set_xticks(x)
ax.set_xticklabels(labels)
ax.legend(fontsize=14)

def autolabel(rects):
    """Attach a text label above each bar in *rects*, displaying its height."""
    for rect in rects:
        height = rect.get_height()
        ax.annotate('{}'.format(height),
                    xy=(rect.get_x() + rect.get_width() / 3, height),
                    xytext=(0, 3),  # 3 points vertical offset
                    textcoords="offset points",
                    ha='center', va='bottom')


autolabel(rects1)
autolabel(rects2)
autolabel(rects3)

fig.tight_layout()

plt.show()

这个代码模块的输出确实是一团糟。但是我期望的效果应该类似于图片中的条形图。您能告诉我代码中哪一点不正确吗？

特伦顿·麦金尼

从注释JohanC，w = 0.8 / 3将解决这个问题，考虑到当前的代码。
但是，生成图可以更轻松地完成 pandas.DataFrame.plot

import pandas as pd
import matplotlib.pyplot as plt

# given the following code to create the dataframe
file="https://s3-api.us-geo.objectstorage.softlayer.net/cf-courses-data/CognitiveClass/DV0101EN/labs/coursera/Topic_Survey_Assignment.csv"
df=pd.read_csv(file,index_col=0)

df.sort_values(by=['Very interested'], axis=0,ascending=False,inplace=True)

df['Very interested']=df['Very interested']/2233
df['Somewhat interested']=df['Somewhat interested']/2233
df['Not interested']=df['Not interested']/2233

# your colors
colors = ['#5cb85c', '#5bc0de', '#d9534f']

# plot with annotations is probably easier
p1 = df.plot.bar(color=colors, figsize=(20, 8), ylabel='Percentage', title="The percentage of the respondents' interest in the different data science Area")
p1.set_xticklabels(p1.get_xticklabels(), rotation=0)

for p in p1.patches:
    p1.annotate(f'{p.get_height():0.2f}', (p.get_x() + p.get_width() / 2., p.get_height()), ha = 'center', va = 'center', xytext = (0, 10), textcoords = 'offset points')