Greetings, 

I would like to calculate tolerancelimits for a series of predicted values 
from nonlinear regression models. I've been using the tolerance package 
but the self-starting functions are not in the derivitive tables. When I 
spellout the functions and supply starting values I repeatedly get an 
error message regardless of the starting values I use (see output below). 
Does anyone have a solution for this problem?

> oh_fit2<-nls(MBB ~ SSfpl(AGE, a, b, c, d))
> oh_fit2
Nonlinear regression model
  model:  MBB ~ SSfpl(AGE, a, b, c, d) 
   data:  parent.frame() 
     a      b      c      d 
 9.308 36.420 67.982 12.815 
 residual sum-of-squares: 46834

Number of iterations to convergence: 9 
Achieved convergence tolerance: 8.727e-06 
> tol<-nlregtol.int(oh_fit2,side = 2, alpha = 0.05, P = 0.95)
The following object(s) are masked from 'temp (position 3)':

    a, b, c, d
Error in deriv.formula(form, beta.names) : 
  Function 'SSfpl' is not in the derivatives table
> oh_fit3<-nls(MBB ~ a + ((b - a)/(1 + exp((c-AGE)/d))), start = list(a = 
10, b = 35, c = 65, d = 10))
> oh_fit3
Nonlinear regression model
  model:  MBB ~ a + ((b - a)/(1 + exp((c - AGE)/d))) 
   data:  parent.frame() 
     a      b      c      d 
 9.307 36.421 67.982 12.815 
 residual sum-of-squares: 46834

Number of iterations to convergence: 9 
Achieved convergence tolerance: 7.474e-06 
> tol<-nlregtol.int(oh_fit3,side = 2, alpha = 0.05, P = 0.95)
Error: Error in nls routine.  Consider different starting estimates 
            of the parameters.  Type help(nls) for more options.

Thank you in advance!

Grant.

___________________________
Grant M. Domke
Forest Inventory and Analysis
U.S. Forest Service
Northern Research Station
1992 Folwell Ave.
St. Paul, MN 55108
Ph: 651.649.5138
Fax: 651.649.5140


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