# Re: st: Help with mathematical operation

 From Joseph McDonnell To statalist@hsphsun2.harvard.edu Subject Re: st: Help with mathematical operation Date Sat, 12 Sep 2009 12:28:34 +0930

```Another way might be to use a tempfile

. clear
. set obs 100
. gen y=_n
. tempfile mytmp
. save `mytmp', replace
. rename y x
. cross using `mytmp'
. sort x y
. gen r=x*y

Cheers

Joseph

On Fri, Sep 11, 2009 at 9:37 PM, Bert Jung <bjung59@gmail.com> wrote:
> 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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>
> *
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>

*
*   For searches and help try:
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*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/
```