[R] Fw: problem with nlsLM function

[akshay kulkarni]

Dear duncan,
                        Sorry to bother you with such a silly mistake!!!!!!!! I didn,t notice it!!!!!
Sent: Tuesday, March 19, 2019 6:01 PM
To: akshay kulkarni; R help Mailing list
Subject: Re: [R] Fw: problem with nlsLM function

On 19/03/2019 8:26 a.m., akshay kulkarni wrote:
>
> dear members,
>                              also,I can provide HM1,HM2 and HM3 if needed....
>
> ________________________________________
> From: R-help <r-help-bounces using r-project.org> on behalf of akshay kulkarni <akshay_e4 using hotmail.com>
> Sent: Tuesday, March 19, 2019 5:43 PM
> To: R help Mailing  list
> Subject: [R] problem with nlsLM function
>
> dear members,
>                      I am getting the "singular gradient error" when I use nls for a function of two variables:
>> formulaDH5
> HM1 ~ (a + (b * ((HM2 + 0.3)^(1/2)))) + (A * sin(w * HM3 + a) +
>      C)
>
> HM1 is the response variable, and HM2 and HM3 are predictors.
>
> The problem is I get the same error even when I use nlsLM(in the minpack.lm package):
>
>> nonlin_modDH5 <- nlsLM(formulaDH5, start = list(a = 0.43143, b = 2,A = 0.09,w = 0.8,a = 0.01,C = 0.94))

You have "a" twice in your start list.  That's bound to cause trouble...

Duncan Murdoch


> Error in nlsModel(formula, mf, start, wts) :
>    singular gradient matrix at initial parameter estimates
>> nonlin_modDH5 <- nlsLM(formulaDH5, start = list(a = 1, b = 2,A = 0.09,w = 0.8,a = 0.01,C = 0.94))
> Error in nlsModel(formula, mf, start, wts) :
>    singular gradient matrix at initial parameter estimates
>> nonlin_modDH5 <- nlsLM(formulaDH5, start = list(a = 1, b = 2,A = 0.09,w = 0.8,a = 0.01,C = 2))
> Error in nlsModel(formula, mf, start, wts) :
>    singular gradient matrix at initial parameter estimates
>
> I came to know that nlsLM converges when nls throws a singular gradient error. What is happening above? Can the problem get  solved if I use nls.lm function(in the minpack.lm package) instead?
>
> very many thanks for your time and effort....
> yours sincerely,
> AKSHAY M KULKARNI
>
>          [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help using r-project.org mailing list -- To UNSUBSCRIBE and more, see
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


	[[alternative HTML version deleted]]