Log-likelihood function

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Bleh
Posts: 2
Joined: Fri Feb 03, 2012 7:21 pm

Log-likelihood function

Postby Bleh » Fri Feb 03, 2012 7:51 pm

Hi, I am trying to solve a time series problem but I am stuck with a function I am not used to work with. I have a basic yt=d +B(yt-1)+e(t) model where e(t) has mean 0 and variance sigma^2. The issue is that (e)t follows the density function that I attached to the post and it's causing me issues because of the gamma function with the (1/L) after. Does anyone know how I need to handle that part of the function to build my log likelihood function for (d,B,o^2) ? What I have tried so far has let me with the following: L=Lambda (is a known parameter), G=gamma function, o is sigma

-2/3 ln 2L - ln G(1/L) - Sum(t=2, T) (yt-d-B(yt-1))^L/(2o^2)^(1/2) - (y1-d/(1-B))^L / (2o^2/(1-B^2))^(1/2)

Is this way of handling the density function with the Gamma correct (basically ignoring it as it goes away after the derivatives)? If not could anyone shed some light on the way I should approach this to solve it?

Thanks a lot.
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EViews Glenn
EViews Developer
Posts: 2682
Joined: Wed Oct 15, 2008 9:17 am

Re: Log-likelihood function

Postby EViews Glenn » Mon Feb 06, 2012 1:43 pm

There's a @gamma and @gammalog function that will do the evaluation for you.

Bleh
Posts: 2
Joined: Fri Feb 03, 2012 7:21 pm

Re: Log-likelihood function

Postby Bleh » Mon Feb 06, 2012 5:47 pm

I am not sure I understand what you mean, could you be a bit more precise? Thanks.

EViews Glenn
EViews Developer
Posts: 2682
Joined: Wed Oct 15, 2008 9:17 am

Re: Log-likelihood function

Postby EViews Glenn » Tue Feb 07, 2012 10:27 am

Maybe I didn't understand your question. I thought you were asking about the gamma portion of your likelihood. I was just noting that there is a function @gamma which will evaluate that portion for you.


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