On Thu, Sep 11, 2008 at 5:42 PM, hadley wickham <[EMAIL PROTECTED]> wrote: > On Thu, Sep 11, 2008 at 11:00 AM, Gabor Grothendieck > <[EMAIL PROTECTED]> wrote: >> See ?cut.Date >> >> In the zoo package see: >> ?as.yearmon >> ?as.yearqtr >> ?aggregate.zoo >> >> and the many examples in: >> ?plot.zoo >> ?xyplot.zoo >> as well as the three zoo vignettes. >> >> Also in the xts package look at >> ?to.period >> >> For regularly spaced series the tis package supports a wide >> variety of time bases and can convert among them. >> >> There are as.zoo.tis and as.tis.zoo routines in zoo and tis; also, >> xts is a subclass of zoo so all these packages can work together. > > Ok, lets take a concrete example: > > dates <- structure(c(8516, 8544, 8568, 8596, 8609, 8666, 8701, 8750, 8754, > 8798, 8811, 8817, 8860, 8873, 8918, 8931, 8966, 9020, 9034, 9056 > ), class = "Date") > >> range(dates) > [1] "1993-04-26" "1994-10-18" > > I want to be able to say: give me a monthly time series that spans > this range - i.e. it should start on 1993-04-01 and continue to > 1994-11-01. I should equally easily be able to say give me a yearly > time series, or every 2 months or every 3 months, or 2 weeks etc. > > I don't think that cut.Date helps because I want to make a new series, > not divide up an existing one, similarly with to.period. as.yearmon,
Use cut.Date like this (assuming the dates variable as in your post): r <- as.Date(cut(range(dates), "month")) # every month seq(r[1], r[2]+32, "month") # every 2nd month seq(r[1], r[2]+32, "2 month") # every 3rd month seq(r[1], r[2]+32, "3 month") # every 2nd week seq(r[1], as.Date(cut(r[2]+32, "month")), "2 week") or with yearmon: rr <- as.yearmon(r) as.yearmon(seq(rr[1], rr[2]+1/12, 1/12)) as.yearmon(seq(rr[1], rr[2]+1/12, 2/12)) as.yearmon(seq(rr[1], rr[2]+1/12, 3/12)) # or if you want the final answer as Date class as.Date(as.yearmon(seq(rr[1], rr[2]+1/12, 1/12))) # etc > as.yearqtr etc, might be helpful but I'd need to stitch them together > myself and they don't return dates so I'd have to convert back for > plotting. plot.zoo doesn't help because all the examples are regular Also both yearmon and yearqtr can be used for plotting -- you don't have to convert them back to Dates just for plotting as zoo provides axis.yearmon and axis.yearqtr and furthermore there is no assumption of regular series needed. plot(as.yearmon(Sys.Date()) + c(0, 5, 7, 20)/12, 1:4) Although in all these examples you do have to combine several functions, if there were a function for every conceivable date manipulation there would be too large a number to remember and its better to have a good set of primitives that are sufficiently powerful that most operations can be done in one or two lines as shown above. ______________________________________________ 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.
