如何确定Matplotlib条形图中的条形顺序 [英] How to determine the order of bars in a matplotlib bar chart

问题描述

假设我们将一些数据读入pandas数据框中:

Suppose we read some data into a pandas data frame:

data1 = pd.read_csv("data.csv", "\t")

内容如下:

然后定义一个函数，该函数应该为我们提供水平条形图，条形图的长度代表值，条形图由键标记.

And then define a function which should give us a horizontal bar chart, where the bar lengths represent values and the bars are labelled with the keys.

def barchart(data, labels):
    pos = arange(len(data))+.5    # the bar centers on the y axis
    barh(pos, data, align='center', height=0.25)
    yticks(pos, labels)

然后我们像这样调用plot函数:

Then we call the plot function like this:

barchart(data1["val"], data1["key"])

这给了我们下面的情节:

which gives us the following plot:

现在，什么决定条的顺序?

Now, what determines the order of the bars?

假设我们希望条以特殊顺序显示，例如[C, A, D, F, E, B]，我们该如何执行呢?

Suppose we want the bars in a special order, say [C, A, D, F, E, B], how can we enforce this?

推荐答案

我修改了条形图的原始版本.为了指定条的顺序，我使用了通过ii列设置的索引:

I modified original version of barchart. To specify order of bars I am using index set via ii column:

import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

def barchart(data, labels):
    pos = np.arange(len(data)) + 0.5  # the bar centers on the y axis
    plt.barh(pos, data.sort_index(), align='center', height=0.25)
    plt.yticks(pos, labels.sort_index())

data1 = pd.DataFrame({'key': list('ABCDE'), 'val': np.random.randn(5)})

new_keys = list('EDACB')
data1['ii'] = [new_keys.index(x) for x in data1.key]

data1 = data1.set_index('ii')
barchart(data1["val"], data1["key"])
plt.show()

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