R help - May 2006 - Function (x) as consecutive values

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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?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

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Paul Chatfield a ?crit :
> 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]]
> 
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