R - convert data.frame to multi-dimensional matrix

Question

From example from a data.frame:

x = data.frame(c(1,1,2,2,3,3), c(1,2,1,2,1,2), c(1,1,1,2,2,2), c(12,14,22,24,34,28))
colnames(x)=c(\"Store\",\"Dept\",\"Year\",\"         


        

Answer 1

Something like :

tapply(X = x[["Sales"]], INDEX = x[setdiff(names(x), "Sales")], FUN = identity)

could work, but it is a bit strange to use tapply with the identity function.