[R] Vectors of years, months, and days to dates?
Richard A. O'Keefe
ok at cs.otago.ac.nz
Tue Jun 8 04:57:23 CEST 2004
Rolf Turner <rolf at math.unb.ca> attacked:
Have you ***any*** evidence that R's procedure degrades
performance, under any circumstances? (Apparently not.) In
that case why are you going on and on about it?
I did the following:
function (y, m, d) as.POSIXlt(chron(julian(y=y, x=m, d=d)))
n <- 100000
y <- sample(1970:2004, n, replace=TRUE)
m <- sample(1:12, n, replace=TRUE)
d <- sample(1:28, n, replace=TRUE)
system.time(ymd.to.POSIXlt(y, m, d))
 8.78 0.10 31.76 0.00 0.00
 14.64 0.13 53.30 0.00 0.00
This was on a 500MHz SunBlade100, a slow machine by today's standards,
using R 1.9.0. There is all the evidence one could reasonably ask for
that going through paste() instead of providing y, m, d as numeric
vectors *does* degrade performance under at least some circumstances.
The cost is less than a factor of 2, but not negligible either.
The standard response to this kind of request is ``R is a
cooperative endeavour. Feel free to contribute.''
Well, ymd.to.POSIXlt is my contribution.
> Is there no one supporting my idea?
Wrong: the idea *is* already supported (all except for one trivial
line of code) by the chron package.
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