[R] how to vectorize a for loop

From: stephen sefick <ssefick_at_gmail.com>
Date: Sun, 09 Nov 2008 22:57:04 -0500


#Is there a way to vectorize the for loop
#maybe a fancy indexing trick?
#thanks

d=0.5
L=20
x=seq(20, by=1, length.out=20)
reflecting <- function(pre, d, L){
	r=L-1
	x=rep(0, L)
	for(j in 2:r){
	x[j]=((1-(2*d))*pre[j])+(d*pre[(j+1)])+(d*pre[(j-1)])
	}
	x[1]=((1-d)*pre[1])+(d*pre[2])
	x[L]=((1-d)*pre[L])+(d*pre[(L-1)])
	y=x

}

f = reflecting(x, d, L)

-- 
Stephen Sefick
Research Scientist
Southeastern Natural Sciences Academy

Let's not spend our time and resources thinking about things that are
so little or so large that all they really do for us is puff us up and
make us feel like gods.  We are mammals, and have not exhausted the
annoying little problems of being mammals.

								-K. Mullis

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Received on Mon 10 Nov 2008 - 04:13:13 GMT

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