st: Collapse (sum) observations by two variables?

[Harriet Baker <hmb7@duke.edu>]

Hello,

I am working on a project with contributors to candidates. I would  
like to sum contributions within a given geographic area (zip code)  
to a given candidate.  If I only had one candidate, then I would  
collapse(sum) amount, by (area).  However, I have over 1000  
candidates in the data.  Is there a way that I can collapse sum with  
two conditions?

My data is structured as follows

Candid  	Amount		Area
1		10			a
1		20			b
1		70			c
1		10			b
2		20			c
2		10			a
2		30			c
2		20			b
3		40			c
3		60			a
3		40			b
3		10			a

I want:

1		a			10
1		b			80
1		c			70
2		a			10
2		b			20
2		c			50

Does anyone know how I might do this? Thank you.

Harriet Baker
Duke University
Political Science
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