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

[stefan.petersson at inizio.se]

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?