Displaying 7 results from an estimated 7 matches for "overparametrization".
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overparameterization
2005 Nov 02
1
model selection based on AICc
Dear members of the list,
I'm fitting poisson regression models using stepAIC that appear to
be overparametrized. I would like to know if there is the
possibility of fitting models by steps but using the AICc instead of
AIC.
Best wishes
German Lopez
2005 Nov 03
1
Help on model selection using AICc
Hi,
I'm fitting poisson regression models to counts of birds in
1x1 km squares using several environmental variables as predictors.
I do this in a stepwise way, using the stepAIC function. However the
resulting models appear to be overparametrized, since too much
variables were included.
I would like to know if there is the possibility of fitting models
by steps but using the AICc
2007 Apr 10
1
nlm() and optim()
Dear R-users,
I have just joint the list and much appreciate any thoughts on 2 issues.
Firstly, I want to reproduce some minimization results conducted in MATLAB. I have suceeded with nlm and optim-method CG. I have been told that I should get also with other optim methods. Actually, I found the same results when testing a very straightforward equation. However with a more complicated model it
2008 Apr 03
1
Lapack error in Design:::ols
Hi,
I'm trying to use Frank Harrell's Design:::ols function to do regression
of y (numeric) on the interaction of two factors (x1 and x2), but Lapack
throws an error:
> library(Design)
...
> load(url("http://www.csse.unimelb.edu.au/~gabraham/x"))
> ols(y ~ x1 * x2, data=x)
Error in chol2inv(fit$qr$qr) : 'size' cannot exceed nrow(x) = 20
> traceback()
2013 May 29
1
quick question about glm() example
I don't have a copy of Dobson (1990) from which the glm.D93 example is
taken in example("glm"), but I'm strongly suspecting that these are
made-up data rather than real data; the means of the responses within
each treatment are _identical_ (equal to 16 2/3), so two of the
parameters are estimated as being zero (within machine tolerance). (At
this moment I don't understand
2010 Mar 30
6
Error "singular gradient matrix at initial parameter estimates" in nls
I am using nls to fit a non linear function to some data.
The non linear function is:
y= 1- exp(-(k0+k1*p1+ .... + kn*pn))
I have chosen algorithm "port", with lower boundary is 0 for all of the
ki parameters, and I have tried many start values for the parameters ki
(including generating them at random).
If I fit the non linear function to the same data using an external
2007 Jan 06
2
negative binomial family glm R and STATA
Dear Lister,
I am facing a strange problem fitting a GLM of the negative binomial
family. Actually, I tried to estimate theta (the scale parameter)
through glm.nb from MASS and could get convergence only relaxing the
convergence tolerance to 1e-3. With warning messages:
glm1<-glm.nb(nbcas~.,data=zonesdb4,control=glm.control(epsilon = 1e-3))
There were 25 warnings (use warnings() to see