Hopefully someone has a good suggestion for your question. I'd just like to point out that the generation of the random walk is pretty much optimized for worst performance.
A 'for' loop is not necessary and growing the objects could be a very significant drag. See Circles 2 and 3 of 'The R Inferno'. Hint: 'cumsum' will be useful. On 02/12/2010 15:58, featherbox wrote:
I've wrote some code to simulate a random walk in 2 dimensions on a lattice. Basically I want to add something in to make it plot it point by point so you can see what is going on. Heres my code for the random walk in 2d RW2D<-function(N) { i<-0 xdir<-0 ydir<-0 xpos<-vector() xpos[1]<-xdir ypos<-vector() ypos[1]<-ydir for (i in 1:N-1) { r<-runif(1) if(r<=0.25) {xdir<-xdir+1} if(r>0.25&& r<=0.5) {xdir<-xdir-1} if(r>0.5&& r<=0.75) {ydir<-ydir +1} if(r>0.75) {ydir<-ydir-1} xpos[i+1]<-xdir ypos[i+1]<-ydir } return(cbind(xpos,ypos)) } rw<-RW2D(10000) xmin<-min(rw[,1]) xmax<-max(rw[,1]) ymin<-min(rw[,2]) ymax<-max(rw[,2]) plot(rw[,1],rw[,2],type="l",xlab="x",ylab="y",main="Random Walk Simulation In Two Dimensions",col="green4",xlim=range(xmin:xmax),ylim=range(ymin:ymax)) end<-cbind(rw[10000,1],rw[10000,2]) start<-cbind(0,0) points(start,pch=4,col="red") points(end,pch=4,col="red")
-- Patrick Burns pbu...@pburns.seanet.com http://www.portfolioprobe.com/blog http://www.burns-stat.com (home of 'Some hints for the R beginner' and 'The R Inferno') ______________________________________________ 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.