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

[Dimitris Rizopoulos]

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

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