R help - May 2010 - problem in using optim

Dear R users,

When I was trying to use the function *optim* to get the MLEs, quite a few
warning messages showed up as below:

Warning in log(psi * lam) : NaNs produced

I am just wondering what does this mean? Was it something wrong with my
likelihood function or was it sth wrong with the data?

Thanks in advance.

Carol Gao

	[[alternative HTML version deleted]]

just check whether some values in the parameter space forcing the log()
function to apply logarithm on negative values !!!
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It probably means that your parameters are taking on values that are
infeasible.  You may have to impose constraints on your parameters to get a
solution (e.g. bounds constraints). If you need better help, you have to
send us a minimal, self-contained, reproducible example.

Ravi.

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
On
Behalf Of Carol Gao
Sent: Friday, May 07, 2010 5:53 AM
To: R-help at r-project.org
Subject: [R] problem in using optim

Dear R users,

When I was trying to use the function *optim* to get the MLEs, quite a few
warning messages showed up as below:

Warning in log(psi * lam) : NaNs produced

I am just wondering what does this mean? Was it something wrong with my
likelihood function or was it sth wrong with the data?

Thanks in advance.

Carol Gao

	[[alternative HTML version deleted]]

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