search for: xy100

...ring problem. I want to extract part of a matrix as a vector, and reorder it to match with an erratic sequence of x,y coordinates. Here's an example that shows what I want and how close I've got (but for some reason my mind just can't get the final step at the moment!): #Define a grid: xy100 <- expand.grid(1:10, 1:10) # Define a matrix ofvalues mat <- matrix(log(xy100[,1]) * log(xy100[,2])+1, ncol = 10)/2 #Plot some the matrix with image and the same data as xy plot: par(mfrow = c(2,2)) image(mat) plot(xy100, cex = c(mat), pch = 20) #define the subset of coordinates I'm int...