Logarithms are being referred to in two contexts here... log of likelihood, and
log of domain variables. I just wanted to highlight that the latter has a
surprisingly simple theoretical basis in optimization.
If you have a function that you want to find an optimum of, but an input
variable need
Section 2 of the vignette for the ordinal package:
https://cran.r-project.org/web/packages/ordinal/vignettes/clm_article.pdf
gives a reasonably complete, if short, definition/discussion of the
log-likelihood framework for ordinal models. It's probably also
discussed in Venables and Ripley
Hi Gregg,
I am sincerely thankful for this workout.
Could you please suggest any text book on how to create log-likelihood
for an ordinal model like this? Most of my online search point me
directly to some R function etc, but a theoretical discussion on this
subject would be really helpful to con
Christofer,
Given the constraints you mentioned—bounded parameters, no intercept, and a sum
constraint—you're outside the capabilities of most off-the-shelf ordinal
logistic regression functions in R like vglm or polr.
The most flexible recommendation at this point is to implement custom
likel
Hello,
Inline.
Às 16:08 de 21/04/2025, Rui Barradas escreveu:
Às 15:27 de 21/04/2025, Brian Smith escreveu:
Hi,
There is a function called RandVec in the package Surrogate which can
generate andom vectors (continuous number) with a fixed sum
The help page of this function states that:
a
Th
Às 15:27 de 21/04/2025, Brian Smith escreveu:
Hi,
There is a function called RandVec in the package Surrogate which can
generate andom vectors (continuous number) with a fixed sum
The help page of this function states that:
a
The function RandVec generates an n by m matrix x. Each of the m
co
RandVec expects both a and b to be single numbers, not numeric vectors
of length > 1.
You could create pairs of (a,b) values and cycle through them. There
are many ways
to do that. Here is one example. (Note that using a=0.1, b=.2, s=1,
n=2 is impossible to achieve, since two numbers bounded above
Hi,
There is a function called RandVec in the package Surrogate which can
generate andom vectors (continuous number) with a fixed sum
The help page of this function states that:
a
The function RandVec generates an n by m matrix x. Each of the m
columns contain n random values lying in the inter
It may be overkill, but package nlsr has function nlxb() that can handle
various models and bound the parameters. Note that bounds can sometimes give
weird results if the bounds and initial parameter guesses are such that the
minimization of the sum of squares gets "stuck".
JN
On 2025-04-21 09:
Hi Gregg,
I thank you for for information about the function vglm()
However it appears that my constraints are a little different.
My parameters have lower and upper bounds and also sum of the
estimated coefficients should be equal to some predefined value.
Other than that, there is no Intercep
Dear R experts,
Thank you all for your help.
Now, I know that the ggplot is causing the issue and that
setting the y=as.numeric(rslt_with_I) can fix the problem,
that should suffice for now, since I am not an R expert.
In addition, this time, I could learn that there is a class
of "AsIs", and th
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