# Re: st: Help with mathematical operation

 From Bert Jung To statalist@hsphsun2.harvard.edu Subject Re: st: Help with mathematical operation Date Fri, 11 Sep 2009 08:07:46 -0400

```Hello Tim,

A brute-force method may be to create multiple datasets (one for each
multiplication) and append them.  Probably not the most efficient
approach but it works:

* Example
clear
set obs 1000

gen x = _n

* Create datasets for y=x*2 ... y=x*4

forvalues i = 2/4 {
preserve
tempfile tmp`i'
gen y = x*`i'
save `tmp`i''
restore
}

* Now return to first dataset and append the others (note that i = 2/4
as in above loop)
gen y = x*1

forvalues i = 2/4 {
append using `tmp`i''
}

sum y

Cheers,
Bert

On Thu, Sep 10, 2009 at 1:18 PM, Burnett, Tim
<Tim.Burnett@ccpanel.gsi.gov.uk> wrote:
> Hello,
>
> I am at the end of my tether with Stata 10 and was hoping someone could help me:
>
> I have a dataset which I am trying to manipulate:
>
> Assuming the following variable:
>
> 1
> 2
> 3
> 4
> 5
> 6
> 7
> 8
>
> I am trying to create a variable which will show:
>
> 1*1
> 1*2
> 1*3
> 1*4
> .
> .
> .
> 2*1
> 2*2
> 2*3
> 2*4
> .
> .
> .
> ...and so on.
>
>
> I really don't know where to look as I can't think what this mathematical operation would be called. Maybe I'm just dim.
>
> Many thanks,
>
> Tim Burnett
>
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```