search for: jmhuttun

Displaying 2 results from an estimated 2 matches for "jmhuttun".

2008 Jun 12
1
Problems with mars in R in the case of nonlinear functions
...t$fitted.values,nrow=nrow(x),byrow=F),ticktype='detailed', col='lightblue', xlab='x',ylab='y',zlab='z',shade=.75,ltheta=50,main='MARS', phi=25,theta=55,zlim=lims) (the code is also here if someone wants to try it: http://venda.uku.fi/~jmhuttun/R/marstest.R) The results are here: http://venda.uku.fi/~jmhuttun/R/R-10.pdf . The fitted model contains only 5 terms which is not enough in this case. Adjusting parameters like nk, thresh, penalty and degree seems only have minor effect or no effect at all. It's also strange that when I in...
2008 Jun 13
1
nls() vs lm() estimates
Hi, I'm trying to understand why the coefficients "a" and "b" for the model: W = a*L^b estimated via nls() differs from those obtained for the log transformed model: log(W) = log(a) + b*log(L) estimated via lm(). Also, if I didn't make a mistake, R-squared suggests a "better" adjustment for the model using coefficients estimated by lm() . Perhaps I'm