[R] Function (x) as consecutive values

[Jacques VESLOT]

sorry, don't understand your problem...
i think it's better to use matrices directly or faster funtions;
but sapply(1:4, function(x) ...) can do the job easily instead of 'for' loops.

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Jacques VESLOT

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Paul Chatfield a écrit :
> Thanks for your reply, though this still wouldn't work with a function 
> for example, starting code like below fails because x is read as a 
> vector as opposed to doing it for x=1 then x=2 - is there any way of 
> tweaking the code easily, or do I just resign myself to for loops to do 
> that?
>  
> x<-1:4
> trial<- function(x)
> {xx<-matrix(runif(20), 2, 10)
> if (xx[1,x]<0.5) { ...}
>  
> Thanks
>  
> Paul
> 
> 
> */Jacques VESLOT <jacques.veslot at good.ibl.fr>/* wrote:
> 
>     ?cumsum
> 
>      > system.time({ z <- NULL ; for (i in 1:1000) z <- c(z,
>     sum((1:i)**2)) })
>     [1] 0.04 0.00 0.04 NA NA
>      > system.time( zz <- cumsum((1:1000)**2) )
>     [1] 0 0 0 NA NA
>      > all.equal(z,zz)
>     [1] TRUE
> 
>     -------------------------------------------------------------------
>     Jacques VESLOT
> 
>     CNRS UMR 8090
>     I.B.L (2ème étage)
>     1 rue du Professeur Calmette
>     B.P. 245
>     59019 Lille Cedex
> 
>     Tel : 33 (0)3.20.87.10.44
>     Fax : 33 (0)3.20.87.10.31
> 
>     http://www-good.ibl.fr
>     -------------------------------------------------------------------
> 
> 
>     Paul Chatfield a écrit :
>      > Hi - I'm trying to avoid using a 'for' loop due to inefficiency
>     and instead use a function (and ultimately tapply as I'm working on
>     a matrix) but I can't figure out how to get 'function' to take the
>     variables as anything other than vectors for example
>      >
>      > aa<-0
>      > x<-1:4
>      > test.fun<-function(x)
>      > {aa<-(x*x +aa)
>      > return(aa)}
>      > test.fun(1:4)
>      >
>      > This code returns 'aa' as 1 4 9 16, but I'd like it to return aa
>     as 1 5 14 30 taking into consideration that I've just calculated aa
>     for x=1. Aside from using loops, is there not a simple way of
>     telling R to work out x for consecutive values?
>      >
>      > thanks
>      >
>      > Paul Chatfield
>      >
>      >
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