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Re: st: dot product across many variables


From   Nick Cox <[email protected]>
To   [email protected]
Subject   Re: st: dot product across many variables
Date   Tue, 29 Nov 2011 18:03:27 +0000

Consider a loop

gen newdummy = 0

forval j = 2000/2010 {
replace newdummy = newdummy + firstdummy`j' * seconddummy`j'
}

On Tue, Nov 29, 2011 at 5:11 PM, Paul Burkander <[email protected]> wrote:

> I have a data set that has two binary variables in each of several
> years.  I'd like to create a new variable that is the sum across all
> years of the product of the two within year.
>
> For example,
> firstdummy2000=1
> seconddummy2000=0
> firstdummy2001=1
> seconddummy2001=1
>
> newdummy=(firstdummy2000*seconddummy2000+firstdummy2001*seconddummy2001)=1
>
> There are so many years that it seems cumbersome to do it as above,
> moreover the years might change over time and I'd like to be flexible.
>
> I thought perhaps a matrix command would work, doing a dot product?
>

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