On 11/09/2007 6:36 AM, Arun Kumar Saha wrote:
> Hi all,
>
> I am looking for a function for following calculation.
>
> start.month = "July"
> end.month = "January"
>
> months = f(start.month, end.month, by=1)
>
> * f is the function that I am looking for.
>
> Actually I want to get months = c("July", "August",.............."January")
>
> If start.month = 6 and end.month = 1 then I could use (not properly) seq()
> function and then I would get month as a vector with elements 6,5,4,3,2, and
> 1 by choosing "by=-1". Is there any function which can subsitute the seq()
> function in my case?
I don't think one already exists, but it's easy to write one:
> cyclic_seq <- function(from, to, cycle=12) {
+ if (to < from) (from - 1):(to + cycle - 1) %% cycle + 1
+ else from:to
+ }
> cyclic_seq(5, 1)
[1] 5 6 7 8 9 10 11 12 1
> cyclic_seq(5, 5)
[1] 5
> cyclic_seq(5, 6)
[1] 5 6
This makes various assumptions about the inputs (e.g. it would fail on
cyclic_seq(20, 1) ); you might want to validate the inputs if you're
giving it to other people.
Duncan Murdoch
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