search for: gnlscontrol

When I run gnls I get the error: Error in nls(y ~ cbind(1, 1/(1 + exp((xmid - x)/exp(lscal)))), data = xy, : step factor 0.000488281 reduced below 'minFactor' of 0.000976563 My first thought was to decrease minFactor but gnlsControl does not contain minFactor nor nlsMinFactor (see below). It does however contain nlsMaxIter and nlsTol which I assume are the analogs of maxiter and tol in nls.control. I would be happy to hear from anyone who has an idea on what parameters in gnlsControl to change to get convergence. Cheers...

Last week (Wed 9/10/2003, "regression questions") I posted a question regarding the use of gnls( ) and its dissimilarity to the syntax that nls( ) will accept. No one replied, so I partly answered my own question by constructing indicator variables for use in gnls( ). The code I used to construct the indicators is at the end of this email. I do have a nagging, unanswered

...argument. However, when I attempt to use the "gnls" function and try to estimate the variance function, as a power function, I get the following error message: > ans51g <- gnls(log(b51) ~ p0 + p1/(1 + exp(-(log(dose)-p2)/p3))^p4, start=list(p0=3,p1=1,p2=4,p3=2,p4=1.5),control=gnlsControl(tol=1.e- 07),weights=varPower()) Error in eval(expr, envir, enclos) : Object "." not found > What am I doing wrong here and how can I do a GLS analysis with a variance function that is estimated from the data? Here is my data: > b51 <- c(17447.60674, 7060.37234, 2872.53012,...

Hi, I am not sure this is a bug but I can repeat it, The functions and data are below. I know this is nasty data, and it is very questionable whether a 4pl model is appropriate, but it is data fed to an automated tool and I would have hoped for an error. Does this repeat for anyone else? My details: > version _ platform i686-pc-linux-gnu

...s? Several work-around exists: * Write a better initial function to get more precise starting values, i.e., fewer iterations needed for nls. * Make a new function my.own.gnls where nls.control(maxiter=100) is set in the call to nls. Maybe it would even be a good idea to pass nlsMaxIter from gnlsControl on to the initial call to nls? As far as I can see from the code it is only used in maximization after the call to get the starting value. Happy R'ing Claus -- ***************************************** Claus Thorn Ekstr?m <ekstrom at dina.kvl.dk> Dept of Mathematics and Physics, KVL...

Hi R-users, Could you give me some advice in solving the problem of such error message from gnls and nls? ## begin error message "Problem in gnls(y1 ~ glogit4(b, c, m, t, x), data.frame(x..: Step halving factor reduced below minimum in NLS step " ##and "Problem in nls(y ~ 1/(1 + exp((xmid - x)/scal)), data = x..: step factor reduced below minimum "? Thank you in