pandas: pivot - 按多列分组

Question

df = pd.DataFrame({'id': ['id1', 'id1','id1', 'id2','id1','id1','id1'],
'activity':['swimming','running','jogging','walking','walking','walking','walking'],
'month':[2,3,4,3,4,4,3]})

pd.crosstab(df['id'], df['activity'])

I'd like to add another column for month in the output to get counts per user within each month for the respective activity.

df.set_index(['id','month'])['activity'].unstack().reset_index()

I get error.

edit: Expected output in the image. I do not know how to create a table.

Answer 1

You can pass a list of columns to pd.crosstab :

x = pd.crosstab([df["id"], df["month"]], df["activity"]).reset_index()
x.columns.name = None

print(x)

Prints:

    id  month  jogging  running  swimming  walking
0  id1      2        0        0         1        0
1  id1      3        0        1         0        1
2  id1      4        1        0         0        2
3  id2      3        0        0         0        1