similar to: Choosing the right model

Displaying 20 results from an estimated 6000 matches similar to: "Choosing the right model"

2011 Aug 09
1
nls, how to determine function?
Hi R help, I am trying to determine how nls() generates a function based on the self-starting SSlogis and what the formula for the function would be. I've scoured the help site, and other literature to try and figure this out but I still am unsure if I am correct in what I am coming up with. ************************************************************************** dat <-
2008 Apr 14
3
Logistic regression
Dear all, I am trying to fit a non linear regression model to time series data. If I do this: reg.logis = nls(myVar~SSlogis(myTime,Asym,xmid,scal)) I get this error message (translated to English from French): Erreur in nls(y ~ 1/(1 + exp((xmid - x)/scal)), data = xy, start = list(xmid = aux[1], : le pas 0.000488281 became inferior to 'minFactor' of 0.000976562 I then tried to set
2004 May 18
0
nlme: Initial parameter estimates
Hello, I am trying to fit a nlme (non linear mixed effect). I am using the SelfStart function SSlogis. However the data in my hand contains few observations per subject (4 or less), so the nlsList doesn't work... In this case I should fixe initial parameter estimates. I remark that values of initial estimates have a greater effect on the model fit (i.e. loglikelihood, AIC and also on
2009 Oct 02
1
nls not accepting control parameter?
Hi I want to change a control parameter for an nls () as I am getting an error message "step factor 0.000488281 reduced below 'minFactor' of 0.000976562". Despite all tries, it seems that the control parameter of the nls, does not seem to get handed down to the function itself, or the error message is using a different one. Below system info and an example highlighting the
2006 May 17
1
nlme model specification
Hi folks, I am tearing my hair out on this one. I am using an example from Pinheiro and Bates. ### this works data(Orange) mod.lis <- nlsList(circumference ~ SSlogis(age, Asymp, xmid, scal), data=Orange ) ### This works mod <- nlme(circumference ~ SSlogis(age, Asymp, xmid, scal), data=Orange, fixed = Asymp + xmid + scal ~ 1, start =
2005 Jun 27
0
SSlogis problem with min(y)==0
Hi, I think this is a problem solved but I would be interested to know if there is some good reason why SSlogis() behaves like this (apologies if this has been noticed before- I'm not confident my archive searches were effective): I have been fitting large numbers of regressions using nls with a self-starting 3 parameter logistic model (SSlogis()). I got a series of unexpected errors of the
2008 Jan 04
3
nls (with SSlogis model and upper limit) never returns (PR#10544)
Full_Name: Hendrik Weisser Version: 2.6.1 OS: Linux Submission from: (NULL) (139.19.102.218) The following computation never finishes and locks R up: > values <- list(x=10:30, y=c(23.85, 28.805, 28.195, 26.23, 25.005, 20.475, 17.33, 14.97, 11.765, 8.857, 5.3725, 5.16, 4.2105, 2.929, 2.174, 1.25, 1.0255, 0.612, 0.556, 0.4025, 0.173)) > y.max <- max(values$y) > model <- nls(y ~
1999 Nov 25
1
gnls
Doug, I have been attempting to learn a little bit about nlme without too much documentation except the online help. The Latex file in the nlme directory looks interesting but uses packages that I do not have so that I have not been able to read it. I have run the example from gnls to compare it with the results I get from my libraries (code below - I have not included output as it is rather
2008 Jan 11
0
nlme model specification (revisit)
Hi List, While using 'nlme' function, I have encountered the similar problem Dr. Stevens and Dr. Graves observed (please see the posts: https://stat.ethz.ch/pipermail/r-help/2006-May/105832.html ). I have tried Dr. Stevens's original example, the problem is still there, > mod.lis <- nlsList(circumference ~ SSlogis(age, Asymp, xmid, scal), + data=Orange ) >
2009 Nov 09
1
Parameter info from nls object
Hi! When checking validity of a model for a large number of experimental data I thought it to be interesting to check the information provided by the summary method programmatically. Still I could not find out which method to use to get to those data. Example (not my real world data, but to show the point): [BEGIN] > DNase1 <- subset(DNase, Run == 1) > fm1DNase1 <- nls(density ~
2001 Jun 01
1
nls works but not gnls
This works fine: fit42<-nls(Vfs~SSlogis(Months,Asym.Int+Asym.Group*Groupdum,xmid,scal), data=df, start=c(Asym.Int=22,Asym.Group=5,xmid=2,scal=6), na.action=na.omit) But this, identical except using gnls, doesn't converge: fit43<-gnls(Vfs~SSlogis(Months,Asym.Int+Asym.Group*Groupdum,xmid,scal), data=df, start=c(Asym.Int=22,Asym.Group=5,xmid=2,scal=6), na.action=na.omit) Error in gnls(Vfs
2004 Aug 10
0
Check failed after compilation (PR#7159)
Full_Name: Madeleine Yeh Version: 1.9.1 OS: AIX 5.2 Submission from: (NULL) (151.121.225.1) After compiling R-1.9.1 on AIX 5.2 using the IBM cc compiler, I ran the checks. One of them failed. Here is the output from running the check solo. root@svweb:/fsapps/test/build/R/1.9.1/R-1.9.1/tests/Examples: ># ../../bin/R --vanilla < stats-Ex.R R : Copyright 2004, The R
2017 Feb 22
0
Crash in the latest release
I found this by accident yesterday. The program that crashes is the first two lines of the example from the help page for nlmer. That example hasn't changed in a long time, so I assumed that it is an R-devel issue. It could also be a long latent nlmer bug. The second run with valgrind is puzzling. Terry T. > library(lmer) > sessionInfo() R Under development (unstable)
2011 Nov 17
3
Obtaining a derivative of nls() SSlogis function
Hello, I am wondering if someone can help me. I have the following function that I derived using nls() SSlogis. I would like to find its derivative. I thought I had done this using deriv(), but for some reason this isn't working out for me. Here is the function: asym <- 84.951 xmid <- 66.90742 scal <- -6.3 x.seq <- seq(1, 153,, 153) nls.fn <- asym/((1+exp((xmid-x.seq)/scal)))
2009 May 04
1
how to change nlme() contrast parametrization?
How to set the nlme() function to return the answer without the intercept parametrization? #========================================================================================= library(nlme) Soybean[1:3, ] (fm1Soy.lis <- nlsList(weight ~ SSlogis(Time, Asym, xmid, scal),                        data = Soybean)) (fm1Soy.nlme <- nlme(fm1Soy.lis)) fm2Soy.nlme <- update(fm1Soy.nlme,
2017 Feb 22
0
[Lme4-authors] Crash in the latest release
Thanks, posted to https://github.com/lme4/lme4/issues/412 for further discussion ... On Wed, Feb 22, 2017 at 10:03 AM, Therneau, Terry M., Ph.D. <therneau at mayo.edu> wrote: > I found this by accident yesterday. The program that crashes is the first > two lines of the example from the help page for nlmer. That example hasn't > changed in a long time, so I assumed that it is
2004 Aug 19
0
NLME: Holding constant the across group correlational structure of the fixed effects in nlme
Hello all. I was wondering if there is a way to hold constant the fixed effects correlation structure across multiple groups? For example, I have two groups and I fit a three parameter logistic growth curve where the fixed effects are free to vary across the groups. I'll paste in the code as a concrete example: > Result.NLME <- nlme(Score ~ SSlogis(Time, Asym, xmid, scal), +
2001 Aug 08
1
NLME augPred error
Could someone explain the meaming of this error message from augPred: > augPred(area3.pen.nlme, primary=~day) Error in predict.nlme(object, value[1:(nrow(value)/nL), , drop = FALSE], : Levels 1,2,3 not allowed for block > predict.nlme(area3.pen.nlme) does not produce an error. area3.pen.nlme was created with: > area3.pen.nlme <- nlme(area ~ SSlogis(day, Asym, xmid, scal),
2005 Jul 26
1
evaluating variance functions in nlme
Hi, I guess this is a final plea, and maybe this should go to R-help but here goes. I am writing a set of functions for calibration and prediction, and to calculate standard errors and intervals I need the variance function to be evaluated at new prediction points. So for instance fit<-gnls(Y~SSlogis(foo,Asym,xmid,scal),weights=varPower())
2009 Jul 30
1
Continue to finish for loop even there is an error in one of rounds.
I am trying to fit a logistic model to my 10 year data (1999-2008) by year. Codes like below: Year <- c(1999: 2008) for(y in 1:length(year)) { file.input <- paste("C:\\", year[y], "\\data.csv", sep="") table <- read.csv(file=fileinput, header=TRUE, as.is=TRUE, na.strings=c("")) initial <- getInitial(percent ~ SSlogis(age, Asym,