changing value of observations to cumulative version over time for each id

[leila salarpour]

Hi Guys,
I have a panel of frequencies looking like
# ID Year Freq
1 1 2000 2
2 1 2001 3
3 1 2002 2
4 2 2000 0
5 2 2001 3
6 2 2002 5
I have more than 2000 IDs and around 20 years. I want to change this to a cumulative version where for each id values of freq will sum up over time like
Version 2
# ID Year Freq
1 1 2000 2
2 1 2001 5
3 1 2002 7
4 2 2000 0
5 2 2001 3
6 2 2002 8
I think I can switch my panel to a wide version and then sum the values using a loop, but I was wondering if there are any other ways to approach this problem in this long format.
And if I have to switch it to wide, what would be the best way I can define my loop to go over years for each id and sum the values year by year?
Thanks for the help.
Leila

[Carole J. Wilson]

Use -sum()- within the -gen- command:

* Example generated by -dataex-. To install: ssc install dataex
clear
input float(num ID Year Freq wanted_freq)
1 1 2000 2 2
2 1 2001 3 5
3 1 2002 2 7
4 2 2000 0 0
5 2 2001 3 3
6 2 2002 5 8
end

bysort ID (Year) : gen cum_freq=sum(Freq)

[Nick Cox]

See also

help cumul

[leila salarpour]

Thanks a lot!