R rep function with for loop

Question

I have a year range 1981:1984. How can use rep() function to get the following results: For each round rep, the latest year is dropped off: first get 1981:1984, then 1981:1983, then 1981:1982, then 1981 as shown in the table:

why use `rep` for this task? `unlist(sapply(1:4, function(i){1981:(1985-i)}))` would do the trick. — Jealie, Apr 03 '17 at 18:17

score 8 · Answer 1 · answered Apr 03 '17 at 18:18

8

One way:

v = 1981:1984
v[ sequence(rev(seq_along(v))) ]
# [1] 1981 1982 1983 1984 1981 1982 1983 1981 1982 1981

answered Apr 03 '17 at 18:18

Frank

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R rep function with for loop

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