[R] psi not functioning in nlrob?

[Xiao Xiao]

Thank you Keo!
After installing MASS the default "psi=psi.huber" is working now.
However I still can't get "psi=psi.bisquare" to work, and here's
another error message:
> model3=nlrob(y~a1*x^a2,data=transient,psi=psi.bisquare, start=list(a1=0.02,a2=0.7),maxit=1000)
Error in na.fail.default(list(y = c(71.2600034232749, 148.175742933206,  :
  missing values in object

I don't know why there are missing values, I'm sure y is the right
length and there are no NAs in it. Could somebody help me with this
one please?

Thanks in advance,
Xiao
On Wed, Aug 12, 2009 at 11:47 PM, Keo
Ormsby<christopher.ormsby at cieni.org.mx> wrote:
> 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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>
>