Duncan Murdoch-2 wrote:
>
> 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
>
And the rest would be to use month.name or month.abb variables
month.name[cyclic_seq(7,1)]
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