> code (C in this case). What exactly are you asking? You can alway > 'time' (sys.time) a set of statements to see which is better (just > make sure you execute them enough times to get reasonable readings -- > several seconds)
I was wondering where to seach for the code of these different options to realize where the differences between them are. The fact is that I have implemented some code to change an image (big matrix), by calling .C and the for I mentioned in this first mail: (a) for (i in 1:length(data)){ data[i] <- table[data[i]+1] } My C function performs practically the same: (b) for (i = 0; i < size; i++){ image[i] = table[image[i]]; } and I used Rprof to discover that, by running both of these functions, one after the other, the first one (a) uses 99.6 aprox of the CPUs time and (b) the other 0.4 So, the first I asked is to improve (a) which I got yours answers (and will test these days). My question is, why is (b) so much faster than (a) (and I think also faster than the solution you guys gave to me, but that is my opinion)? Hope this is clear, (I managed my poor English as well as I could) Thanks again, Walter ______________________________________________ R-help@r-project.org 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.