At Tue, 20 Nov 2007 12:53:31 +1100, John Pye wrote: > I have a question about the use of the gsl_multifit_linear routine that > perhaps is a question more about geometry/algebra than coding, but I'm > not sure. > > I want to construct a routine that fits a plane (in three dimensions) > through a set of data points (x,y,z). I have set up gsl_multifit_linear > to fit the plane equation a*x + b*y + c*z = 1to my data, and for most > cases that seems to work OK. However there are a few degenerate cases > that don't work, and I'm trying to work out what I should do. Is there a > better equation that describes a plane?
Hello, In the general case of this problem you need orthogonal regression (which is not something GSL has at the moment) -- i.e. minimisation of the orthogonal distance to the plane. It's more complicated than linear regression. Linear regression only works if the model is written with a dependent variable, i.e. z = a*x + b*y + c, or similar. This minimises the residual in the chosen direction -- if that's acceptable then you can use linear regression. -- Brian Gough Network Theory Ltd, Publishing Free Software Manuals --- http://www.network-theory.co.uk/ _______________________________________________ Help-gsl mailing list Help-gsl@gnu.org http://lists.gnu.org/mailman/listinfo/help-gsl
