On Sat, Sep 11, 2010 at 12:49 AM, Waichler, Scott R <scott.waich...@pnl.gov> wrote: > 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. > > Thanks, > Scott Waichler
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) Or have I missed something? Barry _______________________________________________ R-sig-Geo mailing list R-sig-Geo@stat.math.ethz.ch https://stat.ethz.ch/mailman/listinfo/r-sig-geo
