Displaying 20 results from an estimated 3000 matches similar to: "parameterization of gnls model"
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
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
2004 Jun 07
2
MCLUST Covariance Parameterization.
Hello all (especially MCLUS users).
I'm trying to make use of the MCLUST package by C. Fraley and A. Raftery. My problem is trying to figure out how the (model) identifier (e.g, EII, VII, VVI, etc.) relates to the covariance matrix. The parameterization of the covariance matrix makes use of the method of decomposition in Banfield and Rraftery (1993) and Fraley and Raftery (2002) where
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
2013 Jan 22
0
ordering in 'gnls' with 'corCompSymm' corStruct
Dear R-devel members,
While writing a new correlation structure similar to 'corCompSymm' and
intended to be used with 'gnls', I got puzzled with the 'Initialize' method.
Using 'Initialize' before 'gnls' may be regarded as a mean to set an
initial value for the corStruct parameter. However 'gnls' does not work
properly with a
2004 Dec 01
0
gnls(0 error: invalid variable type
Dear R-helpers;
While using gnls() to fit a function
> Gbht0t.gnls <- gnls(h2 ~ Rht(b0, b1, b2, h1,t1, t2), data=gbht10,
+ params=list(b0 + b1 + b2 ~ Sisp -1), start=c(strssb0,strssb1,strssb2))
I encountered an error:
"Error in model.frame(formula, rownames, variables, varnames, extras,
extranames, : invalid variable type "
Rht is a defined function to be
2005 Mar 02
1
Using varPower in gnls, an answer of sorts.
Back on January 16, a message on R-help from Ravi Varadhan described a
problem with gnls using weights=varPower(). The problem was that the
fit failed with error
Error in eval(expr, envir, enclos) : Object "." not found
I can reliably get this error in version 2.0.1-patched 2004-12-09 on
Windows XP and 2.0.1-Patched 2005-01-26 on Linux.
The key feature of that example is that the
2003 Jul 24
0
nls.control in gnls
Hi,
I've made a selfStart function for use with gnls and the
following piece of code works nicely:
check1 <- gnls(y ~ spot.shape.fct(xcord, ycord, background, spotintensity,
rho, sigma, delta, mux, muy),
start=getInitial(y ~ spot.shape.fct(xcord, ycord,
background, spotintensity, rho,
2009 Oct 30
0
Interpreting gnls() output in comparison to nls()
Hi,
I've been trying to work with the gnls() function in the "nlme" package. My
decision to use gnls() was so that I could fit varPower and such to some of
the data. However, in working with a small dataset, I've found that the
results given by gnls() don't seem to make any sense and they differ
substantially from those produced by nls(). I suspect that I am just
2012 Feb 13
0
Error from GNLS (undefined columns selected)
Dear R-helpers,
I'm a new R-user and I was trying to gain some experience with the GNLS function of the NLME package.
This is an extract from my dataset (it's a 432x6 data.frame) called "input", in the first column I have the values that I need to fit, while the remaining columns are input variables for the theoretical model, the function "mymodel" (which returns a
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>
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
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]]
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
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
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
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:
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
2006 Feb 17
0
trouble with extraction/interpretation of variance struct ure para meters from a model built using gnls and varConstPower
Works perfectly. Thank you.
-Hugh Rand
-----Original Message-----
From: Spencer Graves [mailto:spencer.graves at pdf.com]
Sent: Sunday, January 15, 2006 6:41 PM
To: Rand, Hugh
Cc: 'r-help at lists.R-project.org'
Subject: Re: [R] trouble with extraction/interpretation of variance
structure para meters from a model built using gnls and varConstPower
How about this:
>
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