[R] Function (x) as consecutive values

[Jacques VESLOT]

?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
>    
> 
> Send instant messages to your online friends http://uk.messenger.yahoo.com 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>