在列中显示特定值的唯一计数，使用 pandas 按附加列分组

Question

I have a dataset, df, where I would like to group by one column, reveal the counts of each unique value and display the proper column.

data

Id      location
e-db    ny
e-db    ny
e-db    ny
f-a     ny
f-a     ny
gr-x    ca

desired

Id      location    count
e-db    ny          3
f-a     ny          2
gr-x    ca          1

doing

df.groupby('location')['Id'].nunique()

However, this is not showing me the unique Id's and the actual value. Any suggestion is appreciated

Answer 1

You can also do this:

df2 = pd.DataFrame()
df2['location'] = df.groupby('Id')['location'].nth(0)
df2['count'] = df.groupby('Id').count()

Output:

Id  location    count
e-db    ny       3
f-a     ny       2
gr-x    ca       1