Displaying 20 results from an estimated 2000 matches similar to: "nls with some coefficients fixed"
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
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 ~
2012 Oct 22
3
Error: object 'CO2' not found
Hello:
I am new on R, this is the first time I work with it,
I am trying to run some R example to get learn of them,
but, I have a problem when running the example below:
http://stat.ethz.ch/R-manual/R-patched/library/datasets/html/zCO2.html
CO2.Qn1 <- CO2[CO2$Plant == "Qn1", ]
SSasympOff(CO2.Qn1$conc, 32, -4, 43) # response only
Asym <- 32; lrc <- -4; c0 <- 43
2004 Jul 16
1
Does AIC() applied to a nls() object use the correct number of estimated parameters?
I'm wondering whether AIC scores extracted from nls() objects using
AIC() are based on the correct number of estimated parameters.
Using the example under nls() documentation:
> data( DNase )
> DNase1 <- DNase[ DNase$Run == 1, ]
> ## using a selfStart model
> fm1DNase1 <- nls( density ~ SSlogis( log(conc), Asym, xmid, scal ),
DNase1 )
Using AIC() function:
>
2012 Jan 20
1
nobs() and logLik()
Dear all,
I am studying a bit the various support functions that exist for
extracting information from fitted model objects.
From the help files it is not completely clear to me whether the number
returned by nobs() should be the same as the "nobs" attribute of the
object returned by logLik().
If so, then there is a slight inconsistency in the methods for 'nls'
objects with
2012 Sep 19
0
Discrepancies in weighted nonlinear least squares
Dear all,
I encounter some discrepancies when comparing the deviance of a weighted and
unweigthed model with the AIC values.
A general example (from 'nls'):
DNase1 <- subset(DNase, Run == 1)
fm1DNase1 <- nls(density ~ SSlogis(log(conc), Asym, xmid, scal), DNase1)
This is the unweighted fit, in the code of 'nls' one can see that 'nls'
generates a vector
2013 Feb 12
0
Deviance and AIC in weighted NLS
Dear All,
I encounter some discrepancies when comparing the deviance of a weighted and
unweigthed model with the AIC values. A general example (from 'nls'):
DNase1 <- subset(DNase, Run == 1)
fm1DNase1 <- nls(density ~ SSlogis(log(conc), Asym, xmid, scal), DNase1)
Now for a weighted fit:
fm2DNase1 <- nls(density ~ SSlogis(log(conc), Asym, xmid, scal),
2006 Sep 11
4
syntax of nlme
Hello,
How do I specify the formula and random effects without a startup object
? I thought it would be a mixture of nls and lme.
after trying very hard, I ask for help on using nlme.
Can someone hint me to some examples?
I constructed a try using the example from nls:
#variables are density, conc and Run
#all works fine with nls
DNase1 <- subset(DNase, Run == 1 )
fm2DNase1 <- nls(
2004 Jul 16
0
Does AIC() applied to a nls() object use the correctnumber of estimated parameters?
Thanks Adaikalavan, however the problem remains.
Considering AIC() as applied to the linear model in AIC() help
documentation:
> data(swiss)
> lm1 <- lm(Fertility ~ . , data = swiss)
> AIC(lm1)
[1] 326.0716
Clearly this includes the estimation of the residual standard error as
an estimated parameter, as this gives the correct score:
> -2*logLik(lm1) + 2*(length(coef(lm1))+1)
2005 Apr 23
1
start values for nls() that don't yield singular gradients?
I'm trying to fit a Gompertz sigmoid as follows:
x <- c(15, 16, 17, 18, 19) # arbitrary example data here;
y <- c(0.1, 1.8, 2.2, 2.6, 2.9) # actual data is similar
gm <- nls(y ~ a+b*exp(-exp(-c*(x-d))), start=c(a=?, b=?, c=?, d=?))
I have been unable to properly set the starting value '?'s. All of
my guesses yield either a "singular gradient" error if they
2010 Apr 12
0
How to derive function for parameters in Self start model in nls
Dear all
i want to fit the self start model in nls. i have two question. i have a
function,
(asfr ~ I(((a*b)/c))+ ((c/age)^3/2)+ exp((-b^2)*(c/age)+(age/c)-2)
i am wondering how to build the selfstart model. there is lost of example,
(i.e. SSgompertz, SSmicman, SSweibull, etc). my question is, how to derive
the function of parameters. and also which model to use for get
the initials values. In the
2011 Jun 17
2
Non-linear Regression best-fit line
I am trying to fit a curve to a cumulative mortality curve (logistic) where y is the cumulative proportion of mortalities, and t is the time in hours (see below). Asym. at 0 and 1
> y
[1] 0.00000000 0.04853859 0.08303777 0.15201970 0.40995074 0.46444992 0.62862069 0.95885057 1.00000000
[10] 1.00000000 1.00000000
> t
[1] 0 13 20 24 37 42 48 61 72 86 90
I tried to find starting values for
2017 Apr 01
6
Intervalos de confianza de la varianza de los residuos en un modelo no lineal.-
Hola amigos,
Supongamos que se quiere ejecutar un modelo no lineal con nls. Pensemos en
el ejemplo de la ayuda:
DNase1 <- subset(DNase, Run == 1)
fm1DNase1 <- nls(density ~ SSlogis(log(conc), Asym, xmid, scal), DNase1)
summary(fm1DNase1)
Aquí se está modelando la densidad óptica de un ensayo relacionada de forma
no lineal (logística) con (el logaritmo) de la concentración de una
proteína.
2006 Jul 18
2
Using corStruct in nlme
I am having trouble fitting correlation structures within nlme. I would like to
fit corCAR1, corGaus and corExp correlation structures to my data. I either
get the error "step halving reduced below minimum in pnls step" or
alternatively R crashes.
My dataset is similar to the CO2 example in the nlme package. The one major
difference is that in my case the 'conc' steps are
2010 Nov 26
1
How to save a data set as .txt on fly?
Hi folks,
Win7 64bit
I tried to save DNase, a data set on database, as .txt file for future use with
load.
I can't do it on fly;
> save(DNase, file="C:/Users/satimis/Documents/aaa.txt")
> load(file="C:/Users/satimis/Documents/aaa.txt")
> aaa
Error: object 'aaa' not found
> aaa.txt
Error: object 'aaa.txt' not found
I must perform following
2013 Jan 04
2
(no subject)
Hi,
I am using the nls function and it stops because the number of iterations
exceeded 50, but i used the nls.control argument to allow for 500
iterations. Do you have any idea why it's not working?
fm1 <- nls(npe ~ SSgompertz(npo, Asym, b2, b3),
data=f,control=nls.control(maxiter=500))
Error in nls(y ~ exp(-b2 * b3^x), data = xy, algorithm = "plinear", start =
c(b2 =
2009 Jun 11
1
formula for degrees of freedom for nonlinear mixed model in nlme
Dear forum members,
What is the formula to calculate denominator degrees of freedom (den df) for nonlinear mixed-effect models with covariates? My model is similar to a CO2 uptake example from Pinheiro and Bates (2000, page 376). In this CO2 dataset, there are two treatments and two types (84 observations in total), but den df for each parameter of the model is 64. Isn’t it too high?
Your
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,
2013 Jan 03
1
nls problem with iterations
Hi,
I am using the nls function and it stops because the number of
iterations exceeded 50, but i used the nls.control argument to allow for
500 iterations. Do you have any idea why it's not working?
fm1 <- nls(npe ~ SSgompertz(npo, Asym, b2, b3),
data=f,control=nls.control(maxiter=500))
Thanks for your help,
Cheers,
Karine.
2000 Oct 14
2
Access to calculations in nls
Hi,
I would like to be able to access the calculated results from the nls package.
Using the example in R, fm3DNase1 we can reurn certain parts of the
calculations:
> coef(fm3DNase1)
Asym xmid scal
2.345179 1.483089 1.041454
> resid(fm3DNase1)
[1] -0.0136806237 -0.0126806237 0.0089488569 0.0119488569 -0.0025803222
[6] 0.0064196778 0.0026723396 -0.0003276604