How could I calculate frequencies in past XX days?

[Han Jin]

Hi All:

Now I want to know in past 45 days, how many different ID appear in my form. For example, data in 2016-2-15 shows _freq from 2016-1-1 to 2016-2-15, data in 2016-2-16 shows _freq from 2016-1-2 to 2016-2-16

First I want to use cumulative frequencies and gen date=_N, then use( _n-45) but cannot deal with repeat ID.

sample:

ID DAY _freq
1 1 1
2 2 2
3 3 3
1 4 3
5 5 4
... ... ...
5 45
6 46
2 47
3 48

Thank you so much to view.

[Nick Cox]

See https://www.statalist.org/forums/for...nge-by-inrange for what looks like the same question.

[Han Jin]

See https://www.statalist.org/forums/for...nge-by-inrange for what looks like the same question.

Hi Nick

You are so helpful, thank you so much.