在工作日重新订购熊猫系列

Question

使用 Pandas，我提取了一个 CSV 文件，然后创建了一系列数据，以找出一周中哪些日子发生的崩溃最多：

crashes_by_day = bc['DAY_OF_WEEK'].value_counts()

然后我将其绘制出来，但当然它以与系列相同的排名顺序绘制它们。

crashes_by_day.plot(kind='bar')

将这些重新排列为周一、周二、周三、周四、周五、周六、周日的最有效方法是什么？

我必须把它分解成一个列表吗？谢谢。

Answer 1

您可以使用Ordered Categorical，然后使用sort_index：

print bc
   DAY_OF_WEEK    a    b
0       Sunday  0.7  0.5
1       Monday  0.4  0.1
2      Tuesday  0.3  0.2
3    Wednesday  0.4  0.1
4     Thursday  0.3  0.6
5       Friday  0.4  0.9
6     Saturday  0.3  0.2
7       Sunday  0.7  0.5
8       Monday  0.4  0.1
9      Tuesday  0.3  0.2
10   Wednesday  0.4  0.1
11    Thursday  0.3  0.6
12      Friday  0.4  0.9
13    Saturday  0.3  0.2
14      Sunday  0.7  0.5
15      Monday  0.4  0.1
16     Tuesday  0.3  0.2
17   Wednesday  0.4  0.1
18    Thursday  0.3  0.6
19      Friday  0.4  0.9
20    Saturday  0.3  0.2

bc['DAY_OF_WEEK'] = pd.Categorical(bc['DAY_OF_WEEK'], categories=
    ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday', 'Sunday'],
    ordered=True)

print bc['DAY_OF_WEEK']
0        Sunday
1        Monday
2       Tuesday
3     Wednesday
4      Thursday
5        Friday
6      Saturday
7        Sunday
8        Monday
9       Tuesday
10    Wednesday
11     Thursday
12       Friday
13     Saturday
14       Sunday
15       Monday
16      Tuesday
17    Wednesday
18     Thursday
19       Friday
20     Saturday
Name: DAY_OF_WEEK, dtype: category
Categories (7, object): [Monday < Tuesday < Wednesday < Thursday < Friday < Saturday < Sunday]

crashes_by_day = bc['DAY_OF_WEEK'].value_counts()
crashes_by_day = crashes_by_day.sort_index()
print crashes_by_day
Monday       3
Tuesday      3
Wednesday    3
Thursday     3
Friday       3
Saturday     3
Sunday       3
dtype: int64

crashes_by_day.plot(kind='bar')

没有Categorical 的下一个可能的解决方案是通过映射设置排序：

crashes_by_day = bc['DAY_OF_WEEK'].value_counts().reset_index()
crashes_by_day.columns = ['DAY_OF_WEEK', 'count']
print crashes_by_day
  DAY_OF_WEEK  count
0    Thursday      3
1   Wednesday      3
2      Friday      3
3     Tuesday      3
4      Monday      3
5    Saturday      3
6      Sunday      3

days = ['Monday','Tuesday','Wednesday','Thursday','Friday','Saturday', 'Sunday']
mapping = {day: i for i, day in enumerate(days)}
key = crashes_by_day['DAY_OF_WEEK'].map(mapping)
print key
0    3
1    2
2    4
3    1
4    0
5    5
6    6
Name: DAY_OF_WEEK, dtype: int64

crashes_by_day = crashes_by_day.iloc[key.argsort()].set_index('DAY_OF_WEEK')

print crashes_by_day
             count
DAY_OF_WEEK       
Monday           3
Tuesday          3
Wednesday        3
Thursday         3
Friday           3
Saturday         3
Sunday           3

crashes_by_day.plot(kind='bar')