# Sample uniformly within a fixed radius.

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## Sample points uniformly within a fixed radius nrand=1000 maxstep=10 ## Sample data ## NB: To get a truly uniform sample over the circle, you must ## sample the square of the distance and then transform back. tempdat<-data.frame(X0=0,Y0=0, bearing0=0, bad.dist= runif(nrand)*maxstep, dist2=sqrt(runif(nrand)*maxstep^2), turningangle=runif(nrand)*2*pi-pi) ##convert Turning angle to bearing (in this case no change) tempdat$bearing=tempdat$bearing0+tempdat$turningangle ## Convert from polar to cartesian coordinates tempdat$X<-tempdat$X0+tempdat$dist2*sin(tempdat$bearing) tempdat$Y<-tempdat$Y0+tempdat$dist2*cos(tempdat$bearing) tempdat$Xbad<-tempdat$X0+tempdat$bad.dist*sin(tempdat$bearing) tempdat$Ybad<-tempdat$Y0+tempdat$bad.dist*cos(tempdat$bearing) ##make plots png(filename="sampleplots.png",width=500,height=1000) par(mfrow=c(2,1)) plot(Ybad~Xbad, data=tempdat, asp=1, main="Center is oversampled") plot(Y~X, data=tempdat, asp=1, main="Uniform across space") dev.off()

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