Faster ways to calculate frequencies and cast from long to wide

You could just use the table command:

table(data$id,data$week)

    1 2 3
  1 2 1 1
  2 0 0 1

If “id” and “week” are the only columns in your data frame, you can simply use:

table(data)
#    week
# id  1 2 3
#   1 2 1 1
#   2 0 0 1