熊猫：用 0 填充一些分类数据

如何解决熊猫：用 0 填充一些分类数据

我有一个带日期的数据集（这可能不是分类数据），我想按星期几（和/或按月或按年，使用相同的逻辑）计算出现次数。>

我有这样的事情，一周中的一天（法语......）：

import numpy as np
import pandas as pd

# this is simulation,of course my datas are more complex ;-)
data = {'date': ["2000-01-01","2000-05-01","2000-11-11","2000-11-01"],'col_2': ['a','b','c','d']}
df = pd.DataFrame.from_dict(data)

# date conversion
df['date'] = pd.to_datetime(df['date'])
df['day_of_week'] = df['date'].dt.day_name(locale = 'fr_FR')

# group by
data = df.groupby('day_of_week')['day_of_week'].agg(['count'])
data.reset_index(level=0,inplace=True)

# order by... order of the day in the week
JOUR_SEMAINE = ["Lundi","Mardi","Mercredi","Jeudi","vendredi","Samedi","Dimanche"]
MAPPING_SEMAINE = {day: i for i,day in enumerate(JOUR_SEMAINE)}

key = data['day_of_week'].map(MAPPING_SEMAINE)
data = data.iloc[key.argsort()]

# see
data

.	day_of_week	计数
0	隆迪	1
1	Mercredi	1
2	萨梅迪	2

这很好，但我如何用 0 填充缺席天数，以获得此：

.	day_of_week	计数
0	隆迪	1
1	狂欢	0
3	Mercredi	1
4	绝地	0
5	vendredi	0
6	萨梅迪	2
7	迪曼奇	0

为了更通用，我正在搜索更自动的方法，为我的分类数组（在本例中为 JOUR_SEMAINE）的每个索引都有一个值，计算值（计数）或 0 ...

有人知道吗？

提前致谢

解决方法

首先，我将创建分类数据框。我们可以使用日历库获取工作日名称。

import pandas as pd
import calendar as cal

weekdays = [wd for wd in cal.day_name]
weekday_count_df = pd.DataFrame(index=weekdays)
weekday_count_df

接下来，我们将您的数据放入数据框中。

data = {'date': ["2000-01-01","2000-05-01","2000-11-11","2000-11-01"],'col_2': ['a','b','c','d']}
data_df = pd.DataFrame(data)
data_df['date'] = pd.to_datetime(data_df['date'])
data_df['day_of_week'] = data_df['date'].dt.day_name()
data_df

接下来，我们可以连接两个数据框。

data_group_df = data_df.groupby('day_of_week')['date'].count()
weekday_count_df = weekday_count_df.join(data_group_df)
weekday_count_df = weekday_count_df.fillna(0)
weekday_count_df

最后，我们可以修复列类型和名称。

weekday_count_df = weekday_count_df.rename(columns={'date':'count'})
weekday_count_df['count'] = weekday_count_df['count'].astype('int32')
weekday_count_df

最终结果是这样的：

            count
Monday      1
Tuesday     0
Wednesday   1
Thursday    0
Friday      0
Saturday    2
Sunday      0