florianhartig / BayesianTools

General-Purpose MCMC and SMC Samplers and Tools for Bayesian Statistics
https://cran.r-project.org/web/packages/BayesianTools/index.html
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AR1 function sd estimate wrongly scaled #259

Open TahminaMojumder opened 8 months ago

TahminaMojumder commented 8 months ago

likelihoodAR1 parameter sd actually fits (1-a) * sd

florianhartig commented 8 months ago

So, this reference https://faculty.washington.edu/ezivot/econ584/notes/armaestimation.pdf gives the following formula for the likelihood

image

Check

TahminaMojumder commented 8 months ago

https://www.google.de/books/edition/Applied_Time_Series_Analysis/9sM3Lpxgr7EC?hl=en&gbpv=1&dq=unconditional+log+likelihood+for+ar1&pg=PA250&printsec=frontcover

Screenshot 2023-10-18 at 15 33 21

florianhartig commented 5 months ago

OK, I think this wasn't resolved yet but we agreed the scaling is wrong and we have to change either help or (preferred) the code?