Did you check if the data in "da" has any NA in the dependent or the
independent data?
Remember that your function llk.mar is going to evaluate dnorm for each pair.
If any of those
pairs has an NA value, your function will return an NA at the end
(sum(c(NA,1,2,3)) = NA)
I would check if the ll
It is indeed a negative value for sigma that causes the issue.
You can check this by inserting this line
if(sigma <= 0 ) cat("Negative sigma=",sigma,"\n")
after the line
mu <- x %*% beta
in function llk.mar
Negative values for sigma can be avoided with the use of a transforma
You can record all arguments and return values of the
calls that optim(par,fn) makes to fn with a function
like the following. It takes your function and makes
a new function that returns the same thing but also
records information it its environment. Thus, after
optim is done you can see its pa
Yanwei!!!
Have you tried to write the likelihood function using log-normal directly?
if you haven't so, you may want to check ?rlnorm
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This is only a guess because I don't have your data:
sigma is must be positive in the dnorm function. My guess is that optim may
attempt an iteration with a negative sigma.
You may want to see help(optim) for dealing with this constraint.
Specifically see the lower argument.
If you specify th
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