Sara Borelli wrote:
I have the following question:
Member Date X
133 04-05-2000 1
133 04-07-2000 4
133 05-06-2000 2
133 07-10-2000 3
145 06-05-2000 5
145 06-15-2000 5
145 08-05-2000 0
145 10-20-2000 2
145 11-05-2000 4
145 12-03-2000 6
Within each member, I need to create a variable that
cumulates the values of X up to the date of the
current observation excluding the value of X of the
current observation, that is I need to create Xnew
such that:
Member Date X Xnew
133 04-05-2000 1 0
133 04-07-2000 4 1
133 05-06-2000 2 5
133 07-10-2000 3 7
145 06-05-2000 5 0
145 06-15-2000 5 5
145 08-05-2000 0 10
145 10-20-2000 2 10
145 11-05-2000 4 12
145 12-03-2000 6 16
--------------------------------------------------------------------
This does it:
sort Member Date
by member: generate Xnew=sum(X)-X
-sum()- calculates the cumulative sum, here within a by-group; see:
help sum()
Hope this helps
Svend
________________________________________________________
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6
DK-8000 Aarhus C, Denmark
Phone, work: +45 8942 6090
Phone, home: +45 8693 7796
Fax: +45 8613 1580
E-mail: [email protected]
_________________________________________________________
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