Мы можем использовать rep
с table
table(rep(seq_len(nrow(mydata)), ncol(mydata)), c(mydata))
data
mydata <- structure(c(3, 3, 1, 1, 1, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 3, 3,
3, 3, 3, 3, 3, 3, 3, 3, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 3,
3, 3, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3), .Dim = c(5L, 10L))