Re: st: Creating interaction and square variables

["Dimitriy V. Masterov" <dvmaster@gmail.com>]

Mike,

You are not understanding how if works. Take a look at this:
http://www.stata.com/help.cgi?ifcmd

Depending on which version of Stata you have, you also might want to
look into factor variable notation to do this for you on the fly.

DVM


On Thu, Aug 30, 2012 at 3:39 PM, Mike Kim <kalisperos@gmail.com> wrote:
> Hi all,
>
> I would like to create interaction and square variables. Let say, I have
> three variables x1, x2, x3.
>
> I used to the following code to create interactions and square of x1, x2,
> x3.
>
> forv i=1/3 {
>   forv j=1/3 {
>   gen x`i'x`j'=x`i'*x`j'    //  if `i'<=`j'   : This still creates variables
> with missing values.
>   }
> }
>
> Since x1*x2 = x2*x1, for example, I tried to drop those same variables using
> the following code, but got error message: "invalid syntax, r(198)".
>
> forv i=1/3 {
>  forv j=1/3 {
>  drop x`i'x`j' if  `i'<`j'
>  }
> }
>
> Can you please let me know what is wrong in the code? Thank you for your
> help in advance.
>
> Mike.
>
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