Hi Jim, > I have been unable to get the sample code that executes the > routine gsl_multilinear_wfit.c (which I literally cut and > pasted from the on-line HTML documentation) to give an answer > that is the same or even close to what is given in the > documentation. > > .... > > My compiled code gives the result > > # best fit: Y = 1.18246 + 0.184573 X + 1.3031 X^2
I also see the result you describe when copy'n'pasting from http://www.gnu.org/software/gsl/manual/html_node/Fitting-Examples.html. FWIW, I can reproduce the 'demo' program output shown earlier in that section. I think there has been a change to the default gsl_rng_env_setup (http://www.gnu.org/software/gsl/manual/html_node/Random-number-environment-variables.html) since when that example was written? Going through rng/ChangeLog I noticed Thu Jul 9 13:56:20 1998 Brian Gough <[email protected]> * default.c (gsl_rng_env_setup): made gsl_rng_mt19937 the default generator but it looks like the fitting example in question was generated in 2001 (http://bzr.savannah.gnu.org/lh/gsl/trunk/revision/2797). A quick sweep through the available random number generators (try setting an incorrect GSL_RNG_TYPE value before running ./generate to get a list) shows that the example in the documentation was produced using the 'mt19937_1999' generator and not the current default. Try running 'GSL_RNG_TYPE=mt19937_1999 ./generate | ./fit 19' to see if it reproduces what the manual documents. It did for me. If it does, please file a bug on savannah asking that either the example be documented with this GSL_RNG_TYPE=mt19937_1999 detail or the results be updated for the new default generator. - Rhys
