search for: ssgompertz

Hi, I am using the nls function and it stops because the number of iterations exceeded 50, but i used the nls.control argument to allow for 500 iterations. Do you have any idea why it's not working? fm1 <- nls(npe ~ SSgompertz(npo, Asym, b2, b3), data=f,control=nls.control(maxiter=500)) Error in nls(y ~ exp(-b2 * b3^x), data = xy, algorithm = "plinear", start = c(b2 = pars[["b1"]], : number of iterations exceeded maximum of 50 Thanks for your help, Cheers, Karine.

I'm using nls to fit a variety of different models. Here I use SSgompertz as an example. I want the ability to fix one (or more) of the coefficients that would normally be optimised (e.g. fix b3=0.8). Examples; based on and using data from example(SSgompertz) #--------------------- # vanilla call to nls, no coefficients fixed, works fine nls(density ~ SSgompertz(log(...

...rror if they are decent guesses, or a "singular gradient matrix at initial parameter estimates" error if they are bad guesses like all zeros. How can I pick starting values that don't result in singular gradients? I have had no luck with the "selfStart" models, e.g., "SSgompertz" -- the formula in "SSgompertz" is not the same as the one I need above, since it has three parameters instead of four. I've tried it and SSfpl thusly: > getInitial(y ~ SSfpl(x,a,b,c,d),data=data.frame(x=x,y=y)) Error in nls(y ~ cbind(1, 1/(1 + exp((xmid - x)/exp(lscal)))),...

Hi everyone, I'm working on a script trying to use foreach %dopar% but without success, so I manage to run the code with foreach %do% and looks like this: The code is part of a MCMC model for projects valuation, returning the most important results (VPN, TIR, EVA, etc.) of the simulation. foreach (simx = NsimT, .combine=cbind, .inorder=FALSE, .verbose=TRUE) %do% { MCPVMPA = MCVAMPA[simx]

...following variables: > x [1] 2 1 1 5 4 6 13 11 13 101 101 101 > y [1] 1.281055090 1.563609934 0.001570796 2.291579783 0.841891853 [6] 6.553951324 14.243274230 14.519899320 15.066473610 21.728809880 [11] 18.553054450 23.722637370 The model fitted was: model<-nls(y~SSgompertz(x,a,b,c)) and it worked OK, with the following results: Formula: y ~ SSgompertz(x, a, b, c) Parameters: Estimate Std. Error t value Pr(>|t|) a 21.2426 0.9689 21.924 4.03e-09 *** b 5.3330 1.4722 3.622 0.00555 ** c 0.8045 0.0274 29.364 3.01e-10 *** Then, trying to...

...data: > x [1] 2 1 1 5 4 6 13 11 13 101 101 101 > y [1] 1.281055090 1.563609934 0.001570796 2.291579783 0.841891853 [6] 6.553951324 14.243274230 14.519899320 15.066473610 21.728809880 [11] 18.553054450 23.722637370 I used nls function with self starters, for example SSgompertz: model<-nls(y~SSgompertz(x,a,b)) The model runs OK, with the following summary: Formula: y ~ SSgompertz(x, a, b, c) Parameters: Estimate Std. Error t value Pr(>|t|) a 21.2426 0.9689 21.924 4.03e-09 *** b 5.3330 1.4722 3.622 0.00555 ** c 0.8045 0.0274 29.364 3....

Dear all i want to fit the self start model in nls. i have two question. i have a function, (asfr ~ I(((a*b)/c))+ ((c/age)^3/2)+ exp((-b^2)*(c/age)+(age/c)-2) i am wondering how to build the selfstart model. there is lost of example, (i.e. SSgompertz, SSmicman, SSweibull, etc). my question is, how to derive the function of parameters. and also which model to use for get the initials values. In the following example's the red color coding requires the explanation?? thanks SSgompertz function (x, Asym, b2, b3) { .expr2 <- b3^x .e...

Hi, I am using the nls function and it stops because the number of iterations exceeded 50, but i used the nls.control argument to allow for 500 iterations. Do you have any idea why it's not working? fm1 <- nls(npe ~ SSgompertz(npo, Asym, b2, b3), data=f,control=nls.control(maxiter=500)) Thanks for your help, Cheers, Karine.

Hi there are some predefined self-start functions, like SSmicmen, SSbiexp, SSasymp, SSasympOff, SSasympOrig, SSgompertz, SSflp, SSlogis, SSweibull, Quadratic, Qubic, SSexp (nlrwr) Btw, do you know graphic examples for this functions? The SSexpDecay (exponential decay) for y = (y0 - plateau)*exp(-k*x) + plateau from http://stats.stackexchange.com/questions/17126/how-can-i-make-my-r-nls-model-more-stable works fine,...

Hi, I have a problem with fitting a nonlinear mixed-effects model to my data. I was able to fit quite simple exponential model but now I?m trying to fit the following Gompertz model: > gomp<-nlme(paino~b0+b1*exp(-exp(-b2*(daydeg.scale-b3))), data=group1, fixed=b0+b1+b2+b3~1, start=c(b0=150, b1=3000, b2=0.6, b3=2500)) I?m getting the following error: Error in chol((value + t(value))/2) :

I am trying to fit a curve to a cumulative mortality curve (logistic) where y is the cumulative proportion of mortalities, and t is the time in hours (see below). Asym. at 0 and 1 > y [1] 0.00000000 0.04853859 0.08303777 0.15201970 0.40995074 0.46444992 0.62862069 0.95885057 1.00000000 [10] 1.00000000 1.00000000 > t [1] 0 13 20 24 37 42 48 61 72 86 90 I tried to find starting values for

...------------------------------------------ Finally, my next step is to automatized the process, with loops, for running each variable with each model in each treatment, which are 4, but i am beginner in R program. Can anyone give a idea about it?. Also, i just tried to use SSmodels, like SSlogis, SSgompertz and SSRichards, but i have models as monomolecular and gauss function that aren't defined in this algoritms. Thanks for your help or suggestions. -- Alejandro Coca UN -------------- next part -------------- DDT TRAT REP ALTURAM NHT NHE NHS PSEUDO DIAM AF PSB PSV PSR PSA PST 23 0 1 0 0.6 1...

...html latex example SSasympOrig text html latex example SSbiexp text html latex example SSfol text html latex example SSfpl text html latex example SSgompertz text html latex example SSlogis text html latex example SSmicmen text html latex example SSweibull text html latex example Theoph text...