[R] comparing elements in a vector

[Liaw, Andy]

If you are only interested in the 2-1 and 1-2 sequence, then the product of
the successive elements must be 2 (i.e., 1*2 = 2*1 = 2).  So try this:

change <- d[-length(d)] * d[-1] == 2

Andy

> -----Original Message-----
> From: Sven Garbade [mailto:garbade at psy.uni-muenchen.de]
> Sent: Wednesday, September 18, 2002 9:35 AM
> To: r-help at stat.math.ethz.ch
> Subject: [R] comparing elements in a vector
> 
> 
> Hi all,
> 
> there is a vector d which contains three different valus: 0, 1 or 2. I
> wrote a loop which gives me T, when the values in d changed from 1 to
> 2 or from 2 to 1, otherwise F:
> 
> for(i in 1:(length(d)-1)) {
>    if(d[i] != d[i+1] & d[i] != 0 & d[i+1] != 0)
>       change[i+1] <- T	    
>     else	  
>       change[i+1] <- F
> }
> 
> This works, but I'm wondering if there is already a R function or an
> easier way to avoid the for-loop.
> 
> Thanks, Sven
> 
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