[R] For-loop dummy variables?

[Bill.Venables at csiro.au]

you might try

dummy <- with(cleary, 
		cbind(B4 = as.numeric(D1 == 4),
			 B6 = as.numeric(D1 == 6),
			 B7 = as.numeric(D1 == 7)))

and do it all in one go.

___

to fix up your apporach you need to use

	if(cleary$D1[i] == 4) dummy[i] <- 1 else dummy[i] <- 0

but this is a very clumsy and slow way of going about it.

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of gravityflyer
Sent: Tuesday, 19 October 2010 1:24 PM
To: r-help at r-project.org
Subject: [R] For-loop dummy variables?


Hi everyone, 

I've got a dataset with 12,000 observations. One of the variables
(cleary$D1) is for an individual's country, coded 1 - 15. I'd like to create
a dummy variable for the Baltic states which are coded 4,6, and 7. In other
words, as a dummy variable Baltic states would be coded 1, else 0.  I've
attempted the following for loop:

dummy <- matrix(NA, nrow=nrow(cleary), ncol=1)
for (i in 1:length(cleary$D1)){
	if (cleary$D1 == 4){dummy[i] = 1}
	else {dummy[i] = 0}
	}

Unfortunately it generates the following error:

1: In if (cleary$D1 == 4) { ... :
  the condition has length > 1 and only the first element will be used


Another options I've tried is the following:

binary <- vector(length=length(cleary$D1))
for (i in 1:length(cleary$D1)) {
	if (cleary$D1 == 4 | cleary$D1 == 6 | cleary$D1 == 7 ) {binary[i] = 1}
 	else {binary[i] = 0}
}

Unfortunately it simply responds with "syntax error".

Any thoughts would be greatly appreciated!


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