Dear List members I am trying to find a way to generate a random point in a circle centred in a geographical location.
So far I have used the following formula (see code below): random_x = original_x + radius*cos(angle) random_y = original_y + radius*sin(angle) where radius is a random number between 0 and the radius of the circle and angle is between 0 and 360 degrees The code bellow works fine however some people argue that this method will produce uneven locations… I really do not understand why. Another option will be to use the “rejection method”: generate points inside a box and reject points that fall outside the circle. However I think this is much complicate… or at least I don’t know how to programme it. So, 1. Is there any package that generates random points in a circle? (I couldn’t find any) 2. Do you think the code bellow produces uneven locations? 3. Any suggestions to programme the “rejection method”? Maybe someone has already used it... Cheers albert #Code random location in a circle # Generate UTM coordinates (original location) > x_utm<-c(289800) > y_utm<-c(4603900) > coord<-as.data.frame(cbind(x_utm,y_utm)) # Generate a random radius with a maximum distance of 1000 meters from the original location. >radius<-runif(1,0,1000) # Generate a random angle >angle<-runif(1,0,360) #Generate a random x coordinate >x_rdm<-coord$x_utm[1]+radius*cos(angle) #Generate a random y coordinate >y_rdm<-coord$y_utm[1]+radius*sin(angle) >result<-as.data.frame(cbind(x_rdm,y_rdm, x_utm, y_utm)) # We can calculate the distance between the original and the random location > result$dist_m<-sqrt(((coord$x_utm-result$x_rdm)^2+(coord$y_utm-result$y_rdm)^2)) >result ______________________________________________ R-help@stat.math.ethz.ch 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.
