On Thu, 29 Sep 2011, Jeff Newmiller wrote:
On Thu, 29 Sep 2011, maxbre wrote:
[With the context excised, something the posting guide expressly asks
not be done.]
yes, you are perfectly right, sorry for that but for me was not so
clear the error message!
A phrase involving pots and kettles springs to mind.
The answer to the question asked was 'see ?julian'
....and the third code example I posted (not working either) should be of
length one (if I'm not wrong again)
but most of all what is not included in my reproducible example and
get a bit confused my question is the case when the variable "date"
contains dates of many years and the objective is to count for each
given year the julian date starting from the first day of the
corresponding year
So you aren't really interested in julian day, you are interested in day of
year. Julian day maps all calendar time to number of days from a SINGLE
epoch (origin) which may differ from one problem to the next, but not from
one value to the next within the problem the way "beginning of year" changes
for each value.
how would you deal with this problem?
test$doy <- as.POSIXlt(test$date)$yday+1
Perhaps, but as described without the +1. The Julian day of the
origin is taken to be day 0.
I think the OP wanted what ISO 8601:2004 calls 'ordinal dates' and of
which Wikipedia says
'This system is sometimes incorrectly referred to as "Julian Date",
whereas the astronomical Julian Date is a sequential count of the
number of days since day 0 beginning 1 January 4713 BC Greenwich noon,
Julian proleptic calendar (or noon on ISO date -4713-11-24 which uses
the Gregorian proleptic calendar with a year [0000]).'
thanks a lot for your help
max
--
Brian D. Ripley, rip...@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272866 (PA)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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