On Sat, 2007-09-15 at 12:11 -0400, Letticia Ramlal wrote:
> Hello
> I was wonderinf if anyone can help me with this problem, it seems
> trivial but for some reason I can not figure it out.
>
> With a single R command complete the following:
> create a vector calles seqvec that repeats the sequence 1, 3,6,
> 10,15,21.( I was trying to use c() but this does not work)
> create a 5-row, 6-column matirx from seqvec wuth each row containg the
> sequence from before
> and complete the two task above in a single step.
If that is just an example of an arbitrary sequence, then the following
does what you want:
> res <- matrix(rep(c(1,3,6,10,15,21), 5), nrow = 5, byrow = TRUE)
> res
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 3 6 10 15 21
[2,] 1 3 6 10 15 21
[3,] 1 3 6 10 15 21
[4,] 1 3 6 10 15 21
[5,] 1 3 6 10 15 21
But if there is something special in the quoted sequence (it is
cumsum(1:6) ), then the following also does what you want:
> res2 <- matrix(rep(cumsum(1:6), 5), nrow = 5, byrow = TRUE)
> res2
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 3 6 10 15 21
[2,] 1 3 6 10 15 21
[3,] 1 3 6 10 15 21
[4,] 1 3 6 10 15 21
[5,] 1 3 6 10 15 21
> all.equal(res, res2)
[1] TRUE
Take a look at ?rep and, although not needed in this case, ?seq for
generating sequences and repeats.
HTH
G
>
> LTR
>
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