Displaying 20 results from an estimated 2000 matches similar to: "nonlinear regression: nls, gnls, gnm, other?"
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
2003 Apr 19
1
nls, gnls, starting values, and covariance matrix
Dear R-Help,
I'm trying to fit a model of the following form using gnls. I've fitted it
using nlsList with the following syntax:
nlsList(Y~log(exp(a0-a1*X)+exp(b0-b1*X))|K,start=list
(a0=6,a1=0.2,b0=4.5,b1=0.001),data=data.frame(Y=y,X=X,K=k)))
which works just fine:
<snip>
Coefficients:
a0 a1 b0 b1
1 5.459381 0.5006811 5.137458 -0.0040548687
2005 Jul 17
1
how to solve the step halving factor problems in gnls and nls
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
2012 Sep 11
1
boot() with glm/gnm on a contingency table
Hi everyone!
In a package I'm developing, I have created a custom function to get
jackknife standard errors for the parameters of a gnm model (which is
essentially the same as a glm model for this issue). I'd like to add
support for bootstrap using package boot, but I couldn't find how to
proceed.
The problem is, my data is a table object. Thus, I don't have one
individual per
2009 Apr 30
0
Categorical variable in a custom nonlin function with gnm
Hi all
I want to construct a generalised nonlinear model (binomial family) using gnm, of the form:
Response = a + b variable1 + c variable2 + d variable3 - d b variable4 - d c variable5,
with the parameters b, c, and d appearing more than once. Hence, I think I need to use a custom nonlin function with gnm.
One of my predictor variables is categorical, so I have created a dummy variable for
2015 Apr 29
2
Formula evaluation, environments and attached packages
Hi!
Some time ago, I replaced calls to library() with calls to
requireNamespace() in my package logmult, in order to follow the new
CRAN policies. But I just noticed it broke jackknife/bootstrap using
several workers via package parallel.
The reason is that I'm running model replicates on the workers, and the
formula includes non-standard terms like Mult() which are provided by
gnm. If gnm
2013 Aug 22
1
Confusion about Depends:, Imports:, Enhances:, import(), inportFrom()
In checking my vcdExtra package, the following NOTE newly appeared
(R-Forge, using R version 3.0.1 Patched (2013-08-20 r63635))
Package in Depends field not imported from: ?gnm?
These packages needs to imported from for the case when
this namespace is loaded but not attached.
In the DESCRIPTION file, I have
Depends: R (>= 2.10), vcd, gnm (>= 1.0.3)
In NAMESPACE:
# we are a vcd
2002 Oct 04
1
gnls from library nlme
Dear all,
I am trying to gain some experience with the function gnls from the nlme
package.
I tried to model the Theophyline data by trying to model the presumed
dependency of
the clearance on the body weight.
This is my function call of gnls:
gnls(conc~SSfol(Dose,Time,lKe,lKa,lCl),data=Theoph,
params=list(lKe~1,lKa~1,lCl~Wt),start=c(-2.4,0.46,-3.22,0.01))
That's been the result:
Error
2009 Jun 24
1
gnls : Rho
Hello list:
How to extract the value of "Rho" from a gnls() object. I am using gnls()
function similar to
res <- gnls(y~SSmicmen(),correlation=corCompSymm(form~1|b),data=dat)
Thanks in advance,
Mahbub.
--
Mahbub Latif
School of Mathematical Sciences
Queen Mary, University of London
United Kingdom
[[alternative HTML version deleted]]
2009 Jan 07
1
Extracting degrees of freedom from a gnls object
Dear all,
How can I extract the total and residual d.f. from a gnls object?
I have tried str(summary(gnls.model)) and str(gnls.model) as well as gnls(), but couldn?t find the
entry in the resulting lists.
Many thanks!
Best wishes
Christoph
--
Dr. rer.nat. Christoph Scherber
University of Goettingen
DNPW, Agroecology
Waldweg 26
D-37073 Goettingen
Germany
phone +49 (0)551 39 8807
fax +49
2008 Sep 27
1
seg.fault from nlme::gnls() {was "[R-sig-ME] GNLS Crash"}
>>>>> "VW" == Viechtbauer Wolfgang (STAT) <Wolfgang.Viechtbauer at STAT.unimaas.nl>
>>>>> on Fri, 26 Sep 2008 18:00:19 +0200 writes:
VW> Hi all, I'm trying to fit a marginal (longitudinal)
VW> model with an exponential serial correlation function to
VW> the Orange tree data set. However, R crashes frequently
VW>
2008 Sep 02
1
Non-constant variance and non-Gaussian errors with gnls
I have been using the nls function to fit some simple non-linear
regression models for properties of graphite bricks to historical
datasets. I have then been using these fits to obtain mean predictions
for the properties of the bricks a short time into the future. I have
also been calculating approximate prediction intervals.
The information I have suggests that the assumption of a normal
2003 Sep 16
2
gnls( ) question
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
2003 Mar 27
2
Question about R^2 in nonlinear models
Dear all
I''m not sure is this question has much sense, but I''m working with nonlinear
models using the nlme library (gnls fit for different groups) and I''m
wondering if I can get the values of R-squared for each fit. I''ll appreciate
any comment.
Thanks in advance
C. Mora
2004 Jan 14
2
Generalized least squares using "gnls" function
Hi:
I have data from an assay in the form of two vectors, one is response
and the other is a predictor. When I attempt to fit a 5 parameter
logistic model with "nls", I get converged parameter estimates. I also
get the same answers with "gnls" without specifying the "weights"
argument.
However, when I attempt to use the "gnls" function and try to
2003 Aug 14
1
gnls - Step halving....
Hi all,
I'm working with a dataset from 10 treatments, each
treatment with 30 subjects, each subject measured 5
times. The plot of the dataset suggests that a
3-parameter logistic could be a reasonable function to
describe the data. When I try to fit the model using
gnls I got the message 'Step halving factor reduced
below minimum in NLS step'. I´m using as the initial
values of the
2006 Oct 25
1
How to specify a constant in gnls{nlme}
Hi All,
I have question about speficifying a constant in gnls() from package nlme.
Here is a testing code:
#############
library(nlme)
x = exp( rnorm(100))
y = 1/(1+x) + rnorm(100)/10
plot( y ~ x)
fm1 = gnls( y ~ 1/(1+(x/v)^w), start=list( v=1, w=1))
a =1; b=1;
fm2 = gnls( y ~ a/(b+(x/v)^w), start=list( v=1, w=1)) #This won't work
because I don't know to set $a$ and $b$ as
2001 Sep 07
3
fitting models with gnls
Dear R-list members,
Some months ago I wrote a message on the usage of gnls (nlme library) and here I come again.
Let me give an example:
I have a 10 year length-at-age data set of 10 fishes (see growth.dat at the end of this message) and I want to fit a von Bertalanffy growth model, Li= Linf*(1-exp(-k*(ti-t0))) where Li = length at age i, Linf= asymptotic length, k= curvature parameter, ti=
2007 Apr 26
1
gnls warning message
Dear R users;
I was trying to fit a nonlinear model using gnls (nlme version 3.1-80,
R 2.5.0, WinXP) and I got the following error and warning message:
Error in gnls(ht ~ a1 * hd * (1 - a2 * exp(-a3 * (dbh/dq2))), data = hdat, :
Step halving factor reduced below minimum in NLS step
In addition: Warning message:
$ operator is deprecated for atomic vectors, returning NULL in:
2010 Feb 17
0
Help with sigmoidal quasi-poisson regression using glm and gnm functions
Hi everyone,
I'm trying to perform the following regressions in order to compare linear
vs. sigmoidal fit of the relationship between my dependent variable (y) and
one explaining parameter (x2), both including the confounding effects of a
third variable (x1):
quasi-pois-lin <- glm(y ~ x1 + x2, family = quasipoisson(link="identity"),
data=fit)
quasi-pois-sig <- gnm(y ~ x1 +