reshape dataframe based on a string split in one column in R

Question

I have the following data structure

ID  Type  Values
1   A     5; 7; 8
2   A     6
3   B     2; 3

and I would like to reshape it to the following using R:

ID  Type  Values
1   A     5
1   A     7
1   A     8
2   A     6
3   B     2
3   B     3

I've been trying to work out how to do it with plyr but without any success. What is the best way to do this?

Answer 1

Since you asked for a plyr solution, here you go:

ddply(df, .(Type), function(foo) {
    values <- unlist(strsplit(c(foo$Values), ";"))
    data.frame(Type = rep(unique(foo$Type), length(values)), Values = values)
    })