How do you map every combination of categorical variables in R?

Question

Using R, is there a way to take a data set and map out every possible combination of every categorical variable?

For example, let\'s say I had 10,000 rows of custom

Answer 1

Create some dummy data:

dataset <- data.frame(
    spend=10*runif(100),
    email=sample(c("yahoo","gmail","hotmail","aol"),100,replace=TRUE),
    browser=sample(c("Mozilla","IE","Chrome","Opera"),100,replace=TRUE),
    country=sample(c("USA","Canada","China","Australia",
      "Egypt","S.Korea","Brazil"),100,replace=TRUE))

Average the spend per combination:

with(dataset,by(spend,list(email,browser,country),mean))

Note the NAs for combinations without entries.

Or turn this into a three-dimensional array:

as.table(with(dataset,by(spend,list(email,browser,country),mean)))