On Fri, Sep 30, 2011 at 4:47 AM, maxbre <mbres...@arpa.veneto.it> wrote: > here is an alternative long and winded solution to the problem sticking on > the julian function of chron package > > test$year <- as.integer(as.character(test$date, "%Y")) > test$month <- as.integer(as.character(test$date, "%m")) > test$day <- as.integer(as.character(test$date, "%d")) > test$hour <- as.integer(as.character(test$date, "%H")) > > test$jday <-julian(test$month,test$day,test$year,origin=c(month=1, day=0, > year=test$year))
Assume: library(chron) ## test data d <- as.chron(c("2000-01-01", "2000-02-01")) ## Then here are a few more approaches: ## 1 with(month.day.year(d), julian(month, day, year, origin = c(1, 0, year))) ## 2 - yearmon represents a year and month as a year + month/12 where ## month is 0 for jan, 1 for feb, etc. library(zoo) as.numeric(d - as.chron(trunc(as.yearmon(d))) + 1) ## 3 as.numeric(format(as.Date(d), "%j")) Or if d is one or more "Date" class dates then #1 still works. #2 works if we replace as.chron with as.Date. #3 can be reduced to as.numeric(format(d, "%j")) and does not require any external packages. or replace as.chron with as.Date if d is one or more "Date" class dates. > > thank you all for helping me in sorting out the problem > > by the way I like very much this very compact solution > test$doy <- as.POSIXlt(test$date)$yday+1 > but on the other hand I'm still struggling to fully understand it, > especially for what is concerning the part after $: so what is $yday for? > > if someone would be so kind to explain me this part I would be very grateful > > a newbie in R > lesson learned > > max > > > -- > View this message in context: > http://r.789695.n4.nabble.com/julian-day-form-POSIXt-object-tp3855885p3859187.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > R-help@r-project.org mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > -- Statistics & Software Consulting GKX Group, GKX Associates Inc. tel: 1-877-GKX-GROUP email: ggrothendieck at gmail.com ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.