... or slightly less verbose:
m1 <- within(m1,major_allele <- ifelse( Freq1 == MAF, Al1, Al2 ))
?within
Cheers,
Bert
On Mon, Nov 29, 2010 at 10:25 AM, Greg Johnson <g...@nosnhoj.org> wrote:
> Jim Moon <moonja <at> ohsu.edu> writes:
>
>> How might one accomplish this using the by() function?
>> m1 is a data frame.
>>
>> # populate column "m1$major_allele"
>> for ( i in 1:length(m1$major_allele)) {
>> if ( m1$Freq1[i] == m1$MAF[i]){
>> m1$major_allele[i] = m1$Al1[i]
>> }
>> else{
>> m1$major_allele[i] = m1$Al2[i]
>> }
>> }
>
> You could use:
>
> m1$major_allele <- ifelse( m1$Freq1 == m1$MAF, m1$Al1, m1$Al2 )
>
> Greg
>
> ______________________________________________
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>
--
Bert Gunter
Genentech Nonclinical Biostatistics
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