RE: [R] R: looping

From: Huntsinger, Reid <reid_huntsinger_at_merck.com>
Date: Sat 21 May 2005 - 02:16:56 EST


Are you sure that's what you want to do? The subscript is a logical vector of length 3, subscripting a 3 x 3 matrix, so you're treating the matrix as a vector (stacked columns) and recycling the indices. The first iteration modifies 6 entries of the matrix.

It looks like you want to replace the entries in the ith column which exceed top[i] by top[i] (lost the ",i" in the subscript expression in copying, perhaps). That could be done in several ways. You can either create a matrix out of top of the same shape as z and then compare element-by-element, with pmin for example, or use the recycling rule. That latter is cleaner if z is transposed, but

> t(pmin(t(z),top))

works.

You could use apply as well, like

> apply(z,1,function(x) pmin(x,top))

to compare each row with the vector top, but you have to transpose the result. I don't see any advantage to this, though.

Reid Huntsinger

-----Original Message-----
From: r-help-bounces@stat.math.ethz.ch
[mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Clark Allan Sent: Friday, May 20, 2005 10:01 AM
To: r-help@stat.math.ethz.ch
Subject: [R] R: looping

hi all

i have a simple question. code is displayed below.

how can i use a vectorised command in order to do this (ie replace the loop)? (ie apply, lapply, sweep, etc)

z<-matrix(c(1:9),3,3)
top<-c(1.5,5.5,9)

for (i in 1:3) z[z[,i]>top[i]]<-top[i]



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https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Sat May 21 02:50:11 2005

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