search for: ssweibul

SSweibull() :  problems with step factor and singular gradient Hello I am working with growth data of ~4000 tree seedlings and trying to fit non-linear Weibull growth curves through the data of each plant. Since they differ a lot in their shape, initial parameters cannot be set for all plants. That’s...

Hi folks, I tried to retain the Weibull distribution using the `nls' function and proceeding along the lines of the example provided in the `SSweibull' help (at least I thought so): t <- (1:200)/100 v <- pweibull(t, shape=3, scale=1) df <- data.frame(Time=t, Value=v) Asym <- 1.0; Drop <- 1.0; lrc <- 0; pwr <- 1 df.estimate <- nls(Value ~ SSweibull(Time, Asym, Drop, lrc, pwr), data=df) But this yields the error...

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, too. But now I search a...

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 .expr4 <- exp(-b2 *...

...20.366385, 22.475717) X11() par(cex=1.6) plot(Joules~Days,xlab="Days after fasting was initiated",ylab="Mean energy per fish (KJ)") model<-nls(joules~a+b*exp(-c*Days),start=list(a=8,b=9,c=-.229), control=list(minFactor=1e-12),trace=TRUE) summary(model) init <- nls(Joules~ SSweibull(Days,Asym,Drop,lrc,pwr), control=list(minFactor=1e-12),data=.GlobalEnv) init Data here is reproducible. As always, thank you...keith -- M. Keith Cox, Ph.D. Alaska NOAA Fisheries, National Marine Fisheries Service Auke Bay Laboratories 17109 Pt. Lena Loop Rd. Juneau, AK 99801 Keith.Cox@noaa.gov...

...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 html latex example asOneSidedFormula text html latex example clearNames text html latex example formula.nls te...