数据帧中的实例计数

Question

我想数一数一个人在一个数据帧中出现的时间。

假设我们的数据集是-

dic = {'firstname':['John','John','John','John','John','Susan','Mike',
                    'Mike','Jacob','David','Jacob','David','Jacob','David','Mike'],
       'lastname':['Smith','Smith','Adams','Adams','Adams','Wilson',
                   'Jones','Jones','White','Miller','Peterson','Miller','White',
                   'Miller','Jones']}
df = pd.DataFrame(dic)
print(df)

输出-

   firstname  lastname
0       John     Smith
1       John     Smith
2       John     Adams
3       John     Adams
4       John     Adams
5      Susan    Wilson
6       Mike     Jones
7       Mike     Jones
8      Jacob     White
9      David    Miller
10     Jacob  Peterson
11     David    Miller
12     Jacob     White
13     David    Miller
14      Mike     Jones

我想数一数一个人在这个数据中按名字和姓氏设置的次数。

期望输出-

   firstname  lastname count
0       John     Smith     2
1       John     Adams     3
2      Susan    Wilson     1
3       Mike     Jones     3
4      Jacob     White     2
5      David    Miller     3
6      Jacob  Peterson     1

Answer 1

尝尝这个,

In [22]: df.groupby(['firstname', 'lastname']).size().reset_index(name='count')

Out[22]:
  firstname  lastname  count
0     David    Miller      3
1     Jacob  Peterson      1
2     Jacob     White      2
3      John     Adams      3
4      John     Smith      2
5      Mike     Jones      3
6     Susan    Wilson      1