[R] nonlinear regression with M estimation

[Ruei-Che Liu]

Hi All,
   Could any one tells me if R or S has the capacity to fit nonlinear 
regression with Huber's M estimation? Any suggestion is appreciated. I was
aware of 'rlm' in MASS library for robust linear regression and 'nls' for 
nonlinear least squares regression, but did not seem to be able to find 
robust non-linear regression function.

   Thanks and regards,

   Ray Liu