On Tue, Nov 9, 2010 at 3:40 PM, Barry Rowlingson <b.rowling...@lancaster.ac.uk> wrote: > On Mon, Nov 8, 2010 at 5:15 PM, Peter Langfelder > <peter.langfel...@gmail.com> wrote: > >> If you also need the z coordinate, it simply the mean of the matrix Z. >> >> zCenter = mean(Z) > > How can that be right? Suppose your mountain is very flat, so that > your mountain is effectively a cube. The Z values are all the same, > and so their mean is the same. However the centre of mass is, by > symmetry, clearly at height/2. > > Similarly suppose your mountain matrix is one large cell value and > all the rest are near zero - the mean Z will be close to zero but the > centre of mass will be almost half way up the single cell value, > because all the near-zeros contribute nothing to the centre of mass > position.
Yup, the z coordinate is wrong. Only the x and y are right. Peter ______________________________________________ R-help@r-project.org 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.
