Date:         Fri, 4 Nov 2005 08:34:01 -0800
Reply-To:     YI <yi_zhu_web@HOTMAIL.COM>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         YI <yi_zhu_web@HOTMAIL.COM>
Organization: http://groups.google.com
Subject:      Create a Roll Over Sum
Comments: To: sas-l@uga.edu
Content-Type: text/plain; charset="iso-8859-1"

Can anyone guide me how to figure out the following problem? Having a
certain variable of data, I want to create another variable that sums
up previous certain number of rows (including the current row) at each
line.
For example:
With data Var1, and starting at row Three (say everything 3 steps), I
want to create a variable Var2 that sums up previous 2 consecutive rows
and the current row of Var1.
Like the following:
Var1    Var2
1
2
3       6       <-- sum(1+2+3)
4       9       <-- sum(2+3+4)
5       12      ... ...
6       15
7       18
8       21
9       24      <--sum(7+8+9)

Thanks!