xts() speed on data with date index

The explanation for the time difference is likely that xts
converts all time indexes to POSIXct internally whereas
zoo works with them in their original form.   Thus the
time difference would be expected to be the conversion time.

Once its converted then xts would likely be faster for those
xts operatoins where the xts code is in C.  In contrast zoo
is 100% R although eventually it is anticipated that portions
of zoo will be in C too.

As xts in a subclass of zoo some of its operations are done
in zoo so in that case there would not be much of a difference
in speed or if xts handles the corresponding operation itself
but in R then it would not be expected that there would be
much difference either.

I like xts because ?subsetting is easier. ?Something like x["2009-08"].
But it seems that xts() is a little slower than zoo() when converting
data with date index instead of time index.

pr<-matrix(rnorm(20000),nrow=5000,ncol=4)
t<-Sys.time()+(1:5000)*24*3600
d<-as.Date(t)
system.time(x<-zoo(pr,t))

? user ?system elapsed
? ? ?0 ? ? ? 0 ? ? ? 0

system.time(x<-zoo(pr,d))

? user ?system elapsed
? ? ?0 ? ? ? 0 ? ? ? 0

system.time(x<-xts(pr,t))

? user ?system elapsed
? ? ?0 ? ? ? 0 ? ? ? 0

system.time(x<-xts(pr,d))

? user ?system elapsed
? 0.34 ? ?0.00 ? ?0.35

Regards,
Michael

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