
Hi, 

It's not just the for loop, you are also growing objects in your code (z). 
Consider ?cumsum

Cheers, 

Romain

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-----Original Message-----
From: r-help-bounces@r-project.org on behalf of tom soyer
Sent: Tue 11/12/2007 11:17
To: r-help@r-project.org
Subject: [R] Alternative to For Loop?
 
Hi,

I am doing a calculation on a long series using a For Loop. Here is an
example of the calculation:

accumulate=function(x){
 y=0
 z=0
 for(i in 1:length(x)){
  y=y+x[i]
  z=c(z,y)

 }
 return(z[2:length(z)])
}

> x=c(1:10)
> x
 [1]  1  2  3  4  5  6  7  8  9 10
> accumulate(x)
 [1]  1  3  6 10 15 21 28 36 45 55
>

Although the For Loop works, looping through an array is time consuming and
inefficient when the series is large. Does anyone know a faster way of doing
the same calculation? Thanks!

-- 
Tom

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