It may be possible to give a solution without a single for loop.
set.seed(1)
v<-sample(1:10,size=1e6,replace=TRUE)
p<-2:4
countinstance<-function(v,p) {
res<-outer(v,p,FUN="==");
apply(res,2,sum)
}
> system.time(replicate(50,countinstance(v,p)))/50
user system elapsed
0.2146 0.0248 0.2403
It is ~50% slower than the "f2" solution given previously ... but it also gives
you a 2D of where the matches are.
These are stored in the "res" variable; use with care with very big datasets.
I wonder whether it is possible to reduce the memory footprint with bit level
operations ...
Christos Argyropoulos
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