[R] psi not functioning in nlrob?

[Keo Ormsby]

You have to install MASS package first.
Hope this does the trick.
Best,
Keo.

Xiao Xiao wrote:
> Hi all,
>
> I'm trying to fit a nonlinear regression by "nlrob":
>
>  model3=nlrob(y~a1*x^a2,data=transient,psi=psi.bisquare,
> start=list(a1=0.02,a2=0.7),maxit=1000)
>
> However an error message keeps popping up saying that the function
> psi.bisquare doesn't exist.
>
> I also tried psi.huber, which is supposed to be the default for nlrob:
>
> model3=nlrob(y~a1*x^a2,data=transient,psi=psi.huber,
> start=list(a1=0.02,a2=0.7),maxit=1000)
>
> But I still got the same error message - psi.huber doesn't exist.
>
> Is the argument "psi" not available in nlrob?
>
> Any help will be appreciated.
>
> Best,
> Xiao Xiao
>
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