Ben Bolker Threaded Open this post in threaded view ♦ ♦ | Report Content as Inappropriate ♦ ♦ Re: NLS "Singular Gradient" Error In reply to this post by Gabor Creating plots Axum All 7 en SPLUS If you can't find a solution on the Knowledge Base then please contact us on the Technical Support Request Form or by email or Antsy permutations Grep lines before after if value of a string is greater than zero When a girl mentions her girlfriend, does she mean it like lesbian girlfriend? This can't be estimated by standard methods, but there is a long history of alternative solutions.

This performs well on data of the form y = f(x, Î¸) + eps (with var(eps) > 0). This is why the standard error in those parameters is so large in the fit above (and the p-values are so high). But in the nls manual page we have:Warning:*Do not use ?nls? How to explain the use of high-tech bows instead of guns When your mind reviews past events How to slow down sessions?

If I try to write a self starting model to reflect this: model3<-with(curve1, nls(Flux~SSasymp(Par, b, (b-a), c))) I get this error: In addition: Warning message: In nls(Flux ~ SSasymp(Par, b, (b A r regression nls share|improve this question asked Aug 21 '13 at 17:52 sessmurda 5218 add a comment| 1 Answer 1 active oldest votes up vote 10 down vote accepted You Some things to try are: - since log(1-Ne/No) is linear in Ne and run an lm(log(1-Ne/No) ~ Ne) and then use the implied values from that or use them as starting The resulting residuals are approximatelynormally distributed with mean 0 and sd ~ 4.23.2) I agree with the comment of Bert on over-parametrization, but againthe model is not overparamterised, and it is

I've read that when using SSasymp: b is 'the horizontal asymptote (a) -the response when x is 0' while c is the rate constant. When your mind reviews past events How neutrons interact if not through an electromagnetic interaction? asked 5 years ago viewed 16376 times active 4 years ago Blog Stack Overflow Podcast #92 - The Guerilla Guide to Interviewing 11 votes Â· comment Â· stats Linked 4 How Axum 12246 'Singular Gradient Matrix' Errors and Nonlinear Regression in Axum.

Moreover, even if you were able to compute the exact minimum norm solution, the Gauss-Newton method would not be guaranteed to converge to a local minimum. This is because its switching between Gauss-Newton and gradient descent is highly robust against far-off-optimal starting values.Â Unfortunately, the standard nls function has no LM implemented, instead it houses the Gauss-Newton Are youclaiming that every single point on the grid fails? The problem here is that your model is over-specified (too many parameters).

you can get > a closed-form expression for the number eaten as a function of the > other parameters using the Lambert W function. Can I only touch other creatures with spells such as Invisibility? Perhaps you know T? If anybody has a little time and patience, any >advice would be really really appreciated. >Thanks, > > >Mihai Nica, ABD >Jackson State University >ITT Tech Instructor >170 East Griffith Street

The equation is derived from Juliano's chapter in Scheiner and Gurevitch (2001) on Functional Responses. Grothendieck Aug 21 '13 at 19:08 OK, got it. Grothendieck 84.7k475153 Thanks, had tried to compute the coefficients using the y ~ aexp(bx) before and was receiving an error, taking the log excellent way to compute starting values, John C Nash at Mar 31, 2010 at 11:26 am ⇧ If you have a perfect fit, you have zero residuals.

I said that an external algorithms fits the model without any problems: with ~ 500,000 data points and 19 paramters (ki in the original equation), it fits the model in less Furthermore, what is your 'curve1' which you submit to nls? –Cleb Aug 19 '15 at 12:08 Since you didn't provide information on what curve1 is, your example is unfortunately Browse other questions tagged r self-study exponential or ask your own question. Now I can see it, it's so evident...

Here is the revised code: c.0 <- min(q24$cost.per.car) * 0.5 model.0 <- lm(log(cost.per.car - c.0) ~ reductions, data=q24) start <- list(a=exp(coef(model.0)[1]), b=coef(model.0)[2], c=c.0) model <- nls(cost.per.car ~ a * exp(b * I took the liberty of formatting your answer, I hope you don't mind. Does TDS know to delete items with delta packages? Notice, though, that if $a$ is positive then $c$ will be less than the smallest expected value of $Y$--and therefore might be a little less than the smallest observed value of

One of the most dreaded is the "singular gradient matrix at initial parameter estimates" which brings the function to a stop because the gradient check in stats:::nlsModel will terminate if the An extended example of a (moderately difficult) nonlinear fit whose initial values can be determined in this way is described in my answer at http://stats.stackexchange.com/a/15769. The solution is unique and the rapidity of convergence is practically independent from the selection of start conditions (with a Corrado at Mar 31, 2010 at 1:13 pm ⇧ Dear JN, If the square root of two is irrational, why can it be created by dividing two numbers?

Ben Bolker ______________________________________________ [hidden email] mailing list https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code. You might also need analogous code to deal with the possibility $a\lt 0$; I leave that as an exercise. John C Nash wrote:If you have a perfect fit, you have zero residuals. more hot questions question feed default about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology Life / Arts Culture / Recreation

I saidthat an external algorithms fits the model without any problems: with ~500,000 data points and 19 paramters (ki in the original equation), itfits the model in less than 1 second. r nls share|improve this question edited Aug 20 '15 at 22:17 DJJ 685823 asked Aug 19 '15 at 11:56 Rachael 83 This error usually happens when you have chosen Apologies if I haven't explained or formatted this very well, this is my first post and I'm not an experienced R user or statistician! As a guess, I would suspect that the error message is due to the NA entry in Flux. –RHertel Aug 19 '15 at 12:43 Sorry about that I should

R-bloggers.com offers daily e-mail updates about R news and tutorials on topics such as: Data science, Big Data, R jobs, visualization (ggplot2, Boxplots, maps, animation), programming (RStudio, Sweave, LaTeX, SQL, Eclipse, The modifications were made so that theÂ formulaÂ is transformed into a function that returns a vector of (weighted) residuals whose sum square is minimized byÂ nls.lm. So, while you know a lot about the ratio b/c, you know nothing at all about b or c individually. Are you claiming that every single point on the grid fails?

Many thanks, Gabor Grothendieck Threaded Open this post in threaded view ♦ ♦ | Report Content as Inappropriate ♦ ♦ Re: NLS "Singular Gradient" Error Your model is not identifiable. It is from Juliano's (2001) Nonlinear Curve Fitting chapter in Scheiner and Gurevitch. How to remove screws from old decking Maximize result of bitwise AND Stochastic gradient descent: why randomise training set more hot questions question feed lang-r about us tour help blog chat I've tried the different algorithms, different starting values and tried to use optim to minimise the residual sum of squares, all to no avail.

up vote 1 down vote favorite I'm trying to run a non linear regression on this data: Flux<-c(192.09536, 199.47616, 137.63245, 133.60358, -89.28360, -23.17639, -27.14659, 107.25287, 52.72565, NA, 167.43277, 113.59047) Par<-c(4.166667e-01, 4.347826e-02, Bert Gunter Genentech Nonclinical Biostatistics -----Original Message----- From: r-help-bounces at r-project.org Bert Gunter at Mar 30, 2010 at 5:45 pm ⇧ Your model is almost certainly over-parameterized (given the data that Take out p3; it's redundant. The only other posts I saw with that had more variables, I tried increasing the number of iterations but that did not succeed.

bsnrh Threaded Open this post in threaded view ♦ ♦ | Report Content as Inappropriate ♦ ♦ Re: NLS "Singular Gradient" Error No success means that I was not successful John C Nash So this is a case of complaining that your diesel car is broken because you ignored the "Diesel fuel only" sign on the filler cap and put in Best, Gabor Grothendieck wrote: -- Corrado Topi PhD Researcher Global Climate Change and Biodiversity Area 18,Department of Biology University of York, York, YO10 5YW, UK Phone: + 44 (0) 1904 328645, This reduces the model to 3 parameters and can see shown that is a reperametrization of the SSasympOff() defined in R (with default start values). "No" is a parameter too, so

On Thu, 1 Jun 2006, Mihai Nica wrote: >Greetings, >I am having a very hard time with a nonlinear regression. Americanism "to care SOME about something" more hot questions question feed lang-r about us tour help blog chat data legal privacy policy work here advertising info mobile contact us feedback Technology