How to create design matrix in r

Question

I have two factors. factor A have 2 level, factor B have 3 level.

How to create the following design matrix?

     factorA1 factorA2 factorB1 factorB         


        

Answer 1

Expanding and generalizing @Ferdinand.kraft's answer:

dat <- data.frame(
    f1 = sample(LETTERS[1:3], 20, TRUE),
    f2 = sample(LETTERS[4:5], 20, TRUE),
    row.names = paste0("id_", 1:20))

covariates <- c("f1", "f2") # in case you have other columns that you don't want to include in the design matrix
design <- do.call(cbind, lapply(covariates, function(covariate){
    apply(outer(dat[[covariate]], unique(dat[[covariate]]), FUN = "=="), 2, as.integer)
}))
rownames(design) <- rownames(dat)
colnames(design) <- unlist(sapply(covariates, function(covariate) unique(dat[[covariate]])))
design <- design[, !duplicated(colnames(design))] # duplicated colnames happen sometimes
design
#       C A B D E
# id_1  1 0 0 1 0
# id_2  0 1 0 1 0
# id_3  0 0 1 1 0
# id_4  1 0 0 1 0
# id_5  0 1 0 1 0
# id_6  0 1 0 0 1
# id_7  0 0 1 0 1