There may very well be a better solution, but this works.

format(strptime(dayofyear, format="%j"), format="%m-%d")

On Tue, Mar 27, 2012 at 11:12 AM, Sam Albers <tonightsthenight@gmail.com>wrote:

> Hello,
>
> I am having trouble figuring out how to convert a Day of Year integer
> back into a Date format. For example I have the following:
>
> date <-
> c('2008-01-01','2008-01-02','2008-01-03','2008-01-04','2008-01-05','2008-01-06','2008-01-07',
>
> '2008-01-08','2008-01-09','2008-01-10','2008-01-11','2008-01-12','2008-01-13','2008-01-14','2008-01-15',
>
> '2008-01-16','2008-01-17','2008-01-18','2008-01-19','2008-01-20','2008-01-21','2008-01-22','2008-01-23')
>
> ## this is then converted into a number corresponding to the day of
> the year like so:
>
> dayofyear <- strptime(date, format="%Y-%m-%d")$yday + 1
>
> ## Now my question is how do I get back to a date format (obviously
> omitting the year).
> ## The end result is that I'd like to be able to have axis labels as
> something like "Month-Day" or just "Month"
> ## instead of just an integers which isn't always intuitive for people
> but I can't seem to figure out how to tell R
> ## to recognize an integer as a date.
>
> Any suggestions?
>
> Many thanks in advance!
>
> Sam
>
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