Python 从 Pandas DataFrame 绘制条形图
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Plot bar graph from Pandas DataFrame
提问by Alfonso
Assuming i have a DataFramethat looks like this:
假设我有一个DataFrame看起来像这样的：
Hour | V1 | V2 | A1 | A2
0 | 15 | 13 | 25 | 37
1 | 26 | 52 | 21 | 45
2 | 18 | 45 | 45 | 25
3 | 65 | 38 | 98 | 14
Im trying to create a bar plot to compare columns V1and V2by the Hour.
When I do:
我试着去创建一个柱状图来比较列V1和V2经Hour。当我做：
import matplotlib.pyplot as plt
ax = df.plot(kind='bar', title ="V comp",figsize=(15,10),legend=True, fontsize=12)
ax.set_xlabel("Hour",fontsize=12)
ax.set_ylabel("V",fontsize=12)
I get a plot and a legend with all the columns' values and names. How can I modify my code so the plot and legend only displays the columns V1and V2
我得到了一个包含所有列的值和名称的图和一个图例。如何修改我的代码，以便绘图和图例仅显示列V1和V2
采纳答案by EdChum
To plot just a selection of your columns you can select the columns of interest by passing a list to the subscript operator:
要仅绘制选定的列，您可以通过将列表传递给下标运算符来选择感兴趣的列：
ax = df[['V1','V2']].plot(kind='bar', title ="V comp", figsize=(15, 10), legend=True, fontsize=12)
What you tried was df['V1','V2']this will raise a KeyErroras correctly no column exists with that label, although it looks funny at first you have to consider that your are passing a list hence the double square brackets [[]].
您尝试过的是，df['V1','V2']这将引发 aKeyError正确地不存在带有该标签的列，尽管起初看起来很有趣，但您必须考虑到您正在传递一个列表，因此使用了双方括号[[]]。
import matplotlib.pyplot as plt
ax = df[['V1','V2']].plot(kind='bar', title ="V comp", figsize=(15, 10), legend=True, fontsize=12)
ax.set_xlabel("Hour", fontsize=12)
ax.set_ylabel("V", fontsize=12)
plt.show()
