[R] Vectors of years, months, and days to dates?

[Peter Dalgaard]

Prof Brian Ripley <ripley at stats.ox.ac.uk> writes:

> 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
> > days.
> > 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
> > characters,
> > 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.

However, considering what goes on in ISOdatetime, one might as well do

  as.Date(paste(years, months, days, sep="-"))


-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
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