[R] Vectors of years, months, and days to dates?
Prof Brian Ripley
ripley at stats.ox.ac.uk
Mon Jun 7 17:44:09 CEST 2004
On Mon, 7 Jun 2004, Shin, Daehyok wrote:
> The interface for dates in R is a little confusing to me.
> I want to create a vector of Date objects from vectors of years, months, and
> One solution I found is:
> years <- c(1991, 1992)
> months <- c(1, 10)
> days <- c(1, 2)
> dates <- as.Date(ISOdate(years, months, days))
> But, in this solution the ISOdate function converts the vectors into
> which can cause serious performance and memory loss
> when the vectors of years, months, and days are huge.
Really? You have measured the loss? A million causes no problem for
example, and what are you going to do with a million dates that is
instantaneous and worthwhile? And a million dates are hardly going to be
unique so you only need to convert the unique values.
> I am quite sure there is much better solution for it. What is it?
Write your own C code, or make a POSIXlt object directly from the numbers
and convert that.
Brian D. Ripley, ripley at 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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