Hi -
I have a longitudinal data set in long form with annual obs

for 6 years on 1450 kids. I am trying to create a cumulative variable

such that the

value for age 10 is the sum of the values at age 9 and age 10, the value

for age 11 is

the sum of the value for 9, 10, & 11 and so on. I can figure out

how to do this in wide form, but I am going to have to repeat it for

about 50

different variables. It would be much easier if I could just keep the

data in long form. I experimented with _n, and by id age, but

couldn't get what I wanted (e.g., for age 11 I could get the sum of age

10 (_n-1) and

age 11, but not age 9, 10, &11).

Once I create this new variable, is there an easy way to repeat the same

thing for 50 different variables? I usually just copy and paste in my do
file, changing

variable names, but lately the do files have gotten rather long. It seems

there is probably an easy way to have it do the same thing over and over

for

different variables, but I can't figure it out.

Thank you in advance for any suggestions...
Sarah
Sarah Mustillo, Ph.D
Center for Developmental Epidemiology
Department of Psychiatry and Behavioral Sciences
Duke University Medical Center
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