Displaying 20 results from an estimated 3000 matches similar to: "Weighted nls"
2003 Oct 30
2
'nls' and its arguments
Dear R experts!
I'd to fit data by 'nls' with me-supplied function 'fcn'.
1) I'd like 'fcn' to accept arbitrary arguments, i.e. I defined it
as f(...) {<body>}. (Ok, that's not actually impotant).
2) Second, I would NOT like to supply every parameter in the formula.
To illustrate this, let's look at the last example of 'nls' help
2008 Nov 03
2
standard errors for predict.nls?
Dear all,
Is there a way to retrieve standard errors from nls models? The help page tells me that arguments
such as se.fit are ignored...
Many thanks and 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 (0)551 39 8806
Homepage http://www.gwdg.de/~cscherb1
2004 Nov 08
2
Nonlinear weighted least squares estimation
Hi there,
I'm trying to fit a growth curve to some data and need to use a weighted least squares estimator to account for heteroscedasticity in the data. A weights argument is available in nls that would appear to be appropriate for this purpose, but it is listed as 'not yet implemented'. Is there another package which could implement this procedure?
Regards,
Robert Brown
2007 Jun 07
2
Nonlinear Regression
Hello
I followed the example in page 59, chapter 11 of the 'Introduction to R'
manual. I entered my own x,y data. I used the least squares. My function has
5 parameters: p[1], p[2], p[3], p[4], p[5]. I plotted the x-y data. Then I
used lines(spline(xfit,yfit)) to overlay best curves on the data while
changing the parameters. My question is how do I calculate the residual sum
of squares.
2011 Apr 20
1
How can I 'predict' from an nls model with a fit specified for separate groups?
Following an example on p 111 in 'Nonlinear Regression with R' by Ritz &
Streibig, I have been fitting nls models using square brackets with the
grouping variable inside. In their book is this example, in which
'state' is a factor indicating whether a treatment has been used or not:
> Puromycin.m1 <- nls(rate ~ Vm[state] *
+ conc/(K[state] + conc), data = Puromycin,
2005 Jul 19
2
Michaelis-menten equation
Dear R users:
I encountered difficulties in michaelis-menten equation. I found
that when I use right model definiens, I got wrong Km vlaue,
and I got right Km value when i use wrong model definiens.
The value of Vd and Vmax are correct in these two models.
#-----right model definiens--------
PKindex<-data.frame(time=c(0,1,2,4,6,8,10,12,16,20,24),
2000 Aug 12
1
Nonlinear regression question
Dear R users
I recently migrated from Statistica/SigmaPlot (Windows) to R (Linux), so
please excuse if this may sound 'basic'.
When running a nonlinear regression (V = Vmax * conc / (Ks + conc), i.e.
Michaelis-Menten) on SigmaPlot, I get the output listed below:
>>>Begin SigmaPlot Output<<<
R = 0.94860969 Rsqr = 0.89986035 Adj Rsqr = 0.89458984
Standard Error of
2003 Oct 28
2
Confidence ellipse for correlation
Hello,
SAS' point and click interface has the option of produce a scatterplot with a
superimposed confidence ellipse for the correlation coefficient. Since I
generally like R so much better, I would like to reproduce this in R. I've
been playing with the ellipse package. In order to have the points and the
ellipse on the same graph I've done the following.
(Load ellipse
2006 Jul 18
4
How can I extract information from list which class is nls
Hello!
I work with :
R : Copyright 2006, The R Foundation for
Statistical Computing
Version 2.3.1 (2006-06-01)
On Windows XP Professional (Version 2002) SP2.
At this moment I use the function "nls" combined
with a selfStar model (SSmicmen, related to
Michaelis-Menten equation, and provided by the
"stats" package).
When I realise the following operation (cf. p 59
of the
2006 Nov 29
3
R2.4 xyplot + panel.number problem
Hi all;
I'm trying to display a 2 panel plot for the Puromycin data from R
with 2 different non-linear models fitted to each group. The problem
is that as far as I know panel.number doesn't work in the latest
version of R. Can anyone give a hint how to solve this?
Here is the code that I used before and now doesn't work
xyplot(rate ~conc| state,Puromycin,
2009 Nov 17
1
Define lm/glm object without evaluating them
For e.g. lm/glm type models I would like to separate model specification and model fitting and then only fit the models later 'when data arrives'. To be specific, I would like make a specification like
m1 <- lm(rate~conc)
m2 <- lm(rate~I(conc^2))
and then later I want to 'put data into' the objects and evaluate (fit the model), e.g. something like
update(m1, data=Puromycin)
2004 May 21
1
Buglet/omission in nls package (PR#6901)
Dear all,
I noticed the following under R 1.8.1 (when nls was still a separate
package) but the same problem occurs under R 1.9.0 (where most (all?)
of nls is now in the stats package):
> data(Puromycin)
> fm <- nls(rate~SSmicmen(conc,b0,b1), Puromycin, subset = state=="treated")
> coef(summary(fm))
NULL
The problem seems to be that summary.nls uses the name
2003 May 22
1
Plot observed vs. fitted values (weighted nls)
Dear WizaRds,
Given the experimental data,
csdata<-data.frame(
time=c(0,1,3,9,20),
conc=c(638.697,395.69,199.00,141.58,112.16)
)
weighted nls is applied,
wt.MM<- function(resp, time,A1,a1,A2,a2)
{
pred <- A1*exp(-a1*time)+A2*exp(-a2*time)
(resp - pred) / sqrt(pred)
}
#
cs.wt <- nls( ~ wt.MM(conc, time,A1,a1,A2,a2), data=csdata,
2010 Dec 01
2
parametric estimators for species richness in R
Dear everyone,
I am doing some work about species richness estimation. Nonparametric estimation (such as Chao1, Jacknife1) can be done just using function "specpool()" and "estimateR()" in package "vegan". The problem is that I can not found any functions for parametric estimation (such as MMMeans, MMruns, Michaelis-Menten). Do you know any function for doing this?
2018 May 18
3
Exporting to text files
I have dose response data analyzed with the package 'drc'.
'summary(mymodel)' prints my kinetic parameters. I want
that text in an ASCII text file. I want to get exactly what I
would get if I copied and pasted from the terminal window.
I've read the documentation on data export to text files here:
2004 Feb 02
1
Robust nonlinear regression - sin(x)/x?
You reall have only one parameter in your model, c = a/b. You can't
identify both a and b from your model, therefore, you should fit the
linear model: lm(z ~ c* sin(x)/x)
Ravi.
----- Original Message -----
From: cstrato <cstrato at aon.at>
Date: Monday, February 2, 2004 2:28 pm
Subject: [R] Robust nonlinear regression - sin(x)/x?
> Dear all
>
> Since I did not receive any
2018 May 18
0
Exporting to text files
?sink
On May 18, 2018 9:47:25 AM PDT, Ed Siefker <ebs15242 at gmail.com> wrote:
>I have dose response data analyzed with the package 'drc'.
>'summary(mymodel)' prints my kinetic parameters. I want
>that text in an ASCII text file. I want to get exactly what I
>would get if I copied and pasted from the terminal window.
>
>I've read the documentation on
2007 Jun 04
0
nls problems
Hi, All:
The following identifies apparent inconsistencies and proposed
fixes between the documentation and the behavior of 'nls'.
Specifically, the help file says 'data' 'Can also be a list'.
However, I got an error when I tried it with a list that could not be
coerced to a data.frame. This is documented in the first example below.
Also, the
2009 Dec 18
2
NLS-Weibull-ERROR
Hello
I was trying to estimate the weibull model using nls after putting OLS
values as the initial inputs to NLS.
I tried multiple times but still i m getting the same error of Error in
nlsModel(formula, mf, start, wts) :
singular gradient matrix at initial parameter estimates.
The Program is as below
> vel <- c(1,2,3,4,5,6,7,8,9,10,11,12,13,14)
> df <- data.frame(conc, vel)
>
2004 Aug 16
2
using nls to fit a four parameter logistic model
Shalini Raghavan
3M Pharmaceuticals Research
Building 270-03-A-10, 3M Center
St. Paul, MN 55144
E-mail: sraghavan at mmm.com
Tel: 651-736-2575
Fax: 651-733-5096
----- Forwarded by Shalini Raghavan/US-Corporate/3M/US on 08/16/2004 11:25
AM -----
Shalini