> > Is there an existing function to compute the coordinates for the center > > of mass of a variable in a 2D or 3D grid, where dx, dy, and dz are known > > for all cells? The mass in each cell varies by location. > > If your data is in a data frame of coordinates x, y, (and maybe z), > and variable W for all cells, and all your cells are the same size, > then its just the weighted average of the coordinate (assuming your > dataframe is the complete grid). So: > > xm = sum(d$x*d$W)/sum(d$W) > ym = sum(d$y*d$W)/sum(d$W)
You're right, it's simple for a grid where dx and dy are constant. Thanks. But if they vary? Scott Waichler _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
