[R] month increment for chron dates

[Gabor Grothendieck]

I don't know if this is any faster but it does not use any loops or apply
so maybe it is.  x is assumed to be a vector chron dates.  Note that
the question is not well specified for days near the end of the month
and I have not addressed that.

with(month.day.year(x), {
	year <- ifelse(month > 9, year + 1, year)
	month <- ifelse(month > 9, month - 9, month + 3)
	chron(paste(month, day, year, sep = "/"))
} )


On 9/18/05, bmw8042 <bmw8042 at verizon.net> wrote:
> I have a vector of over 7,000 chron dates in the format "mm/dd/yy".  I need
> to increment each date in the vector by a standard number of months.
> Lapply with seq.dates is working OK; this increments the vector x by 3
> months:
> 
> dates(unlist(lapply(x, function(g) seq.dates(g, by="months", length=4)[4])))
> 
> But this takes about 55 seconds to run on a Windows XP 1.8 Pentium 512 RAM
> PC with R version 2.0.0
> Can you recommend a more efficient way to do this?
> 
> thanks for your advice
> 
> Brian Winkler
> Controller
> BPS Trade Services
> CGI
> 
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