Hi all,
Here is a patch that significantly speeds up `[.data.frame` operator.
It applies cleanly to both 2.4.0 and svn trunk. Make check was OK for 2.40.
(for svn trunk it fails even without this patch.. ).
What it does - we get rid of class and attr statements that modify incoming
data frame and use explicit calls to .subset and .subset2 instead.
Test case:
N<-100000
T<-data.frame(a=1:N, b=rnorm(N), c=as.character(round(runif(N)*10)))
system.time({X<-0 ; for(i in 1:1000)X<-X+T[i,2]})
Without patch the output on my system is
[1] 8.488 2.436 10.926 0.000 0.000
With this patch the output is:
[1] 1.084 0.624 1.707 0.000 0.000
thank you !
Vladimir Dergachev