[R] the first. from SAS in R

[Charles C. Berry]

On Tue, 23 Nov 2010, Joel wrote:

>
> Is there any similar function in R to the first. in SAS?
>
> What it dose is:
>
> Lets say we have this table:
>
>  a b  c
>  1 1  5
>  1 0  2
>  2 0  2
>  2 0 NA
>  2 9  2
>  3 1  3
>
>
> and then I want do to do one thing the first time the number 1 appers in a
> and something else the secund time 1 appers in a and so on.
>
> so
>
> something similar to:
>
> if first.a {
> a$d<-1
> }else{
> a$d<-0
> }
>
> This would give me
>
>  a b  c b
>  1 1  5 1
>  1 0  2 0
>  2 0  2 1
>  2 0 NA 0
>  2 9  2 0
>  3 1  3 1
>
> Is there such a function in R or anything similar?

See

 	?duplicated

then try

 	a$d <- ifelse( duplicated( a$a ), 0 , 1 )

and

 	a$d.2 <- as.numeric( !duplicated( a$a ) )

HTH,

Chuck

>
>
> thx
>
> //Joel
>
> -- 
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Charles C. Berry                            Dept of Family/Preventive Medicine
cberry at tajo.ucsd.edu			    UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901