[R] gnls error in NLS step

[Yang, Richard]

Dear R-helpers:

	I have a data set (over 21,000 records) which fitted to a nonlinear
function with 5 parameters using nls() without problems. However, when I
fitted it to the same function using glns(), an error occurred:

	Error in gnls(h2 ~ SiAB(b0, b1, b2, b3, b4, b5, h1, t1, t2), data =
lfdnlp1,  : 
            Step halving factor reduced below minimum in NLS step

The following is the printout of the gnls() with verbose = T :

NLS step: RSS =  60051.74 
 model parameters:0.0142528  -0.40339  1.07913  0.708258  -0.35343  0.333127

 iterations: 7 

Convergence:
  params 
1.083799 

NLS step: RSS =  60051.73 
 model parameters:0.0142575  -0.403859  1.07918  0.708292  -0.353546
0.333152  
 iterations: 7 

Convergence:
     params 
0.001160867 
Error in gnls(h2 ~ SiAB(b0, b1, b2, b3, b4, b5, h1, t1, t2), data = lfdnlp1,
: 
        Step halving factor reduced below minimum in NLS step

I changed the nlsTol to 1e-5 (default is 1e-3) without help. Any suggestions
or workaround for the error?  I am using R 1.50 on W2K.

TIA,

Richard


-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-.-
r-help mailing list -- Read http://www.ci.tuwien.ac.at/~hornik/R/R-FAQ.html
Send "info", "help", or "[un]subscribe"
(in the "body", not the subject !)  To: r-help-request at stat.math.ethz.ch
_._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._._