# [R] Combining all possible values of variables into a new...

Dimitris Rizopoulos d.rizopoulos at erasmusmc.nl
Mon Oct 20 16:22:04 CEST 2008

```try this:

x <- c(1,0,0,1,0,0,1,0,0,1)
y <- c(1,3,2,3,2,1,2,3,2,3)
z <- c(1,2,1,2,1,2,1,2,1,2)
d <- data.frame(x, y, z)

ind <- do.call("paste", c(expand.grid(1:2, 1:3, 0:1)[3:1], sep = "\r"))
trg <- do.call("paste", c(d, sep = "\r"))
d\$myvar <- match(trg, ind)

I hope it helps.

Best,
Dimitris

stefan.petersson at inizio.se wrote:
> I'm trying to create a new column in my data.frame where subjects are categorized depending on values on four other columns. In any other case I would just nest a few ifelse statements, however, in this case i have 4*6*2*3=144 combinations and i get weird 'context overflow' errors. So I wonder if there is a more efficient way of doing this.
>
> For illustrational purposes, let's say i have:
>
> x<-c(1,0,0,1,0,0,1,0,0,1)
> y<-c(1,3,2,3,2,1,2,3,2,3)
> z<-c(1,2,1,2,1,2,1,2,1,2)
> d<-as.data.frame(cbind(x,y,z))
>
> and i do:
>
> d\$myvar <- ifelse(d\$x == 0 & d\$y==1 & d\$z==1 , d\$myvar <- 1,
> ifelse(d\$x == 0 & d\$y==1 & d\$z==2 , d\$myvar <- 2,
> ifelse(d\$x == 0 & d\$y==2 & d\$z==1 , d\$myvar <- 3,
> ifelse(d\$x == 0 & d\$y==2 & d\$z==2 , d\$myvar <- 4,
> ifelse(d\$x == 0 & d\$y==3 & d\$z==1 , d\$myvar <- 5,
> ifelse(d\$x == 0 & d\$y==3 & d\$z==2 , d\$myvar <- 6,
> ifelse(d\$x == 1 & d\$y==1 & d\$z==1 , d\$myvar <- 7,
> ifelse(d\$x == 1 & d\$y==1 & d\$z==2 , d\$myvar <- 8,
> ifelse(d\$x == 1 & d\$y==2 & d\$z==1 , d\$myvar <- 9,
> ifelse(d\$x == 1 & d\$y==2 & d\$z==2 , d\$myvar <- 10,
> ifelse(d\$x == 1 & d\$y==3 & d\$z==1 , d\$myvar <- 11,
> ifelse(d\$x == 1 & d\$y==3 & d\$z==2 , d\$myvar <- 12, NA))))))))))))
>
> Suggestions?
>
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>

--
Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus Medical Center

Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
Fax: +31/(0)10/7043014

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