search for: selfstart

Hello, I'm having problems creating and using a selfStart model with nlme. Briefly, I've defined the model, a selfStart object, and then combined them to make a selfStart.default model. If I apply getInitial to the selfStart model, I get results. However, if I try usint it with nls or nlsList, these routines complain about a lack of initial con...

Hello, I'm trying to do some non-linear regression with 2 cell types and 4 tissue type treatments using selfStart models Following Ritz and Streibig (2009), I wrote the following routines: ##Selfstart expDecayAndConstantInflowModel <- function(Tb0, time, aL, aN, T0){ exp(-time*aL)*(T0*aL+(-1+exp(time * aL))*Tb0 * aN)/aL } expDecayAndConstantInflowModelInit <- function(mCall, LHS, data){ print(pa...

Hi All, Another nls related problem (for background, I'm migrating a complicated modelling package from S-plus to R). Below I've reduced this to the minimum necessary to demonstrate my problem (I think); the real situation is more complicated. Two similar selfStart functions, ssA and ssB. The 'initial' function for ssB modifies its arguments a little and then calls getInital for ssA. In addition to the "x" and the fitted coefficients ("Coeff"), ssA and ssB have arguments ("A") which are not the same length as the datafr...

..."~/Documents/R/Wu_data.dat", header=TRUE) # assign variables Z <- Wu[[1]] # N1,60 X <- Wu[[2]] # CSR Y <- Wu[[3]] # ev, % # set the data frame data1<- data.frame(cbind(N,CSR,ev)) # call nls funciton out <- nls(Z~X/(1/(a+b*ev+c*(Y^2))+X/(d+e*exp(f*Y)))-g, data1, selfStart, trace=T) In total there are 59 sets of (X,Y,Z). When I run this script, I got the error message as: parameters without starting value in 'data': a, b, d, e, f, g I don't know what this means. Besides, I use "selfStart" option, such that the nls is supposed to run by...

Hi Everyone, I'm trying to write selfStart non-linear models for use with nls. In these models some combinations of parameter values are illegal; the function value is undefined. That's OK when calling the function directly [e.g. SSmodel(x, pars...)]; I return an appropriate non-value such as NA or Inf. However, when called from n...

Hi Everyone, I posted this a couple of weeks ago with no responses. My interface (via gmane) seemed a bit flakey at the time, so I'm venturing to repost with some additional information. I'm trying to write selfStart non-linear models for use with nls. In these models some combinations of parameter values are illegal; the function value is undefined. That's OK when calling the function directly [e.g. SSmodel(x, pars...)]; it is appropriate to return an appropriate non-value such as NA or Inf. However, w...

Dear listers, I am trying to fit a model using nlsList() using alternately a SSfol() selfstart function or its developped equivalent formulae. This preliminary trial works well mydata<-groupedData(Conc~Tps|Organ,data=mydata) mymod1<-nls(Conc~SSfol(Dose,Tps,lKe,lKa,lCl),data=mydata) as well as a developped form: mymod2<-nls(Conc~Dose * exp(lKe+lKa-lCl) * (exp(-exp(lKe)*Tps)-exp(...

hi all; I'm starting in PDC and need some help, i'm using samba for pdc but without ldap, and all time that a user make login, open a notepad with the content: [.ShellClassInfo] LocalizedResourceName=@%SystemRoot%\system32\shell32.dll,-21787 or [DeleteOnCopy] Owner=cesar Personalized=5 PersonalizedName=My documents and all folder have a document Desktop.ini... someone can say me why

...quot;D"]],'+5.8)^-1.0)') + print(equation) + linear <- lm(as.formula(equation),data=data) + value <- c(exp(coef(linear)[1]), coef(linear)[2], 1.0) + names(value) <- mCall[c("a", "b", "c")] + value + } > > dhexp <- selfStart(dhexp, initial=dhexpInit) > > getInitial(height ~ dhexp(diameter,a,b,c), spruce) [1] "log( height ) ~ I(( diameter +5.8)^-1.0)" a b c 39.78098 -25.34938 1.00000 > > getInitial(I(height-1.3) ~ dhexp(diameter,a,b,c), spruce) [1] "log( I ) ~ I(( di...

Hi Everyone, I'd omitted the non-optional 'parameters' argument to selfStart. Making this change to SSbatch gives the same (successful) result from the two calls to nls. SSbatch<-selfStart( model=function(Batch, Coeffs) { Coeffs[Batch] } ,initial=function(mCall, data, LHS) { # Estimate coefficients as mean of each batch xy <- sortedXyData(mCall[["Batc...

...help pages, but nothing on a strategic level, what general approach should I use? Can someone point me in the right direction? I'm using nls to fit models where some non-optimised parameters are different lengths from the data, often matrices, something like this ... ---------- SSfunc <- selfStart( model = function(x, Coeff, A) { }, initial = function(mCall, data, LHS) { }, parameters = c("Coeff") ) y <- ... x <-... A <- ... nls(y ~ SSfunc(x, Coeff, A), data=...) -------------------- ... where A may be a matrix. This means that A canno...

...in numericDeriv(form[[3]], names(ind), env) : Missing value or an infinity produced when evaluating the model In addition: Warning message: No starting values specified for some parameters. Intializing 'b', 'a' to '1.'. Consider specifying 'start' or using a selfStart model in: nls(fath ~ ((b^2)/(a^2)) * exp((-dist/a)^b), polcurve) #Geometric function >s=nls(fath~((b-1)*(b-2)/a)*((1+dist/a)^-b),polcurve) Error in nlsModel(formula, mf, start, wts) : singular gradient matrix at initial parameter estimates In addition: Warning message: No starting v...

Hi Rick Thanks to Dieter Menne I did manage to solve the problem of imposing bounds on the parameter space duirng an nlsList fit. He suggested using optim to optimize the parameters prior to each fit. This worked well for me as I had a customized selfStart function that then optimized the parameters for each individual separately. if you rewrote your selfStart function as: powrDpltInit <- function(mCall, LHS, data) { xy <- sortedXyData(mCall[["x"]],LHS,data) min.s <- min(y) dif.s <- max(y)-min(y) dplt.s &l...

...don't say anything about your model which would help to help you... nls in package nls, {i.e. you type library(nls)} has so called self-starting models for a few classes of non-linear *regression* models. I don't know if this helps, since nlm() is not only for regression models. type ?selfStart and apropos("^SS") to get a list of predefined selfstarting models, and then, e.g. ?SSlogis Further you may need to learn more about non-linear regression in general. E.g., Bates, D.M. and Watts, D.G. (1988) Nonlinear Regression Analysis and Its Applications; Wiley. and...

Hello, nls-users, is it possible to pass additional parameters to the model function that are known and groupwise constant with nlsList? I could not find something like a "keep this fixed" option in the documentation and the code (my fault...?) The current workaround is to break the problem down into groups and use globals to pass the constant parameters, but it is ugly code and

Hi everyone, I thought that for a selfStart function, these two should be exactly equivalent > nls(Aform, DF) > nls(Aform, DF, start=getInitial(Aform, DF)) but in this example that is not the case in R (although it is in S-plus V6.2) ------------------------------ SSbatch<-selfStart( model=function(Batch, Coeffs) { Coeffs[Batch]...

...nd of beta function with 2 parameters (optimal and maximum temperatures) and the time function is a 2-parameter Weibull. Adjustments with nls or gnls work, but I need to do mixed-effects modeling. It seems like nlme or nlmer need self starting functions, but so far I can't find a way to code a selfstart function with 2 "x" covariates. Is it just impossible? Is there another way? Thanks -- View this message in context: http://r.789695.n4.nabble.com/Custom-nonlinear-self-starting-function-w-2-covariates-tp2286099p2286099.html Sent from the R help mailing list archive at Nabble.com.

Hello there! I got some data with x and y values. there are some y == 0. This is a problem for the selfstarting regression model SSlogis. The regression works if I use a non selfstarting model. The formula is the same. But this needs very detailed information of the starting list. I dont have this Information all the time. An easy solution for selfstart model could be to add 1E-100 to the y==0 values. T...

Hello, I am doing several self-starting growth functions for using with nls(). When I list the self-starting functions included in nls library, for instance, SSlogis, there is: > SSlogis function (input, Asym, xmid, scal) ... <environment: 03476D20> attr(,"class") [1] "selfStart" What is this <environment: 03476D20> instruction? By using deriv() and then Selfstart(), I don't get this, although everything works fine without it. Thanks for help. Best Regards, Philippe Grosjean ...........]<(({?<...............<?}))><.............................

...<- sortedXyData(mCall[["x"]], LHS, data) Linf <- 900 if (Linf != max(xy[,"y"])) Linf <- -Linf K <- 0.3 t0<-0 value <- c(Linf, K, t0) names(value) <- mCall[c("Linf", "K","t0")] value } vonBert <- selfStart(vonBert, initial = vonBertInit) class(vonBert) #Richards Rich <- function(x, Linf, K, t0, m) Linf*(1-exp(-K*(x-t0)))^(1/(1-m)) size ~ Rich(age, Linf, K, t0, m) Rich <-deriv(~ Linf*(1-exp(-K*(x-t0)))^(1/(1-m)), c("Linf","K","t0","m"),functio...