[R] sort() for time/date objects (was: more on date conversion differences in 2.2.1 vs 2.3.1)

From: Achim Zeileis <Achim.Zeileis_at_wu-wien.ac.at>
Date: Sat 12 Aug 2006 - 10:22:55 EST

On Sat, 12 Aug 2006 09:25:10 +1000 paul sorenson wrote:

> With dates I get different results with 2.2.1 and 2.3.1. From my
> somewhat naive point point of view, the 2.2.1 behaviour seems more
> sensible.

Your example below does not really make the source of the problem obvious. I tried to see where the problem comes from and the following seems to happen:
  xtabs() calls factor() calls sort(unique()) for computing the levels And in the last step sort() seems to strip off the "class" attribute, leaving only the underlying numeric vector.

Of course, the functions never claimed to work for "POSIXct" objects, hence you should call xtabs() appropriately, e.g. via   xtabs(V2 ~ as.character(V1), data = t)

However, it might be desirable to have sort() working for time/date objects (such as POSIXct, Date and date). sort() would just have to preserve the class as it did in R 2.2.1. Z

> Running the code below in 2.2.1:
> V1
> 2006-08-01 2006-08-01
> 1 1
>
> With 2.3.1 I get:
> V1
> 1154354400 1154440800
> 1 1
>
> # testdate.R
> t <- read.csv2('testdate.csv', header=FALSE)
> t$V1 <- as.POSIXct(t$V1)
> print(t)
> x <- xtabs(V2 ~ V1, data=t)
> print(x)
>
> # testdate.csv
> 2006-8-1;0;1
> 2006-8-1;1;1
> 2006-8-2;0;1
> 2006-8-2;0;0
> 2006-8-2;1;1
>
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R-help@stat.math.ethz.ch 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. Received on Sat Aug 12 10:25:07 2006

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