Paula,
Just for fun, another way:
## Create 10 by 10 example matrix
set.seed(100)
a <- matrix(sample(c(0,1,2),100, replace=T), nrow=10, ncol=10)
a[1,] <- sample(c(0.25,0.5,0.75),ncol(a), replace=T)
## Use apply to substitiute matrix values by row
b <- apply(a, 1, function(x)
{
row <- x
row[row==0 | row==1] <- -999
row[which(row==2)] <- a[1,which(x==2)]
return(row)
})
## Transpose result matrix
b <- t(b)
Cheers,
Jeremy
Jeremy Hetzel
Boston University
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