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California-Planet-Search / radvel

General Toolkit for Modeling Radial Velocity Data
http://radvel.readthedocs.io
MIT License
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lnprob NaN with MCMC #266

Closed SpaceyCaseyLynn closed 5 years ago

SpaceyCaseyLynn commented 5 years ago

Hi, I have the attached config file, and I keep getting the error lnprob returned NaN when I try to run radvel mcmc -s file. I've tried troubleshooting for a while (+ with my advisor Lauren Weiss) and we can't figure out why. If someone can help out I'd be very grateful. k102.py.zip

Screen Shot 2019-10-21 at 11 15 23 AM
bjfultn commented 5 years ago

The problem here is that the logk parameters are running away to -infinity and essentially causing a floating point overflow. This can happen when working in the logk basis with poor constraints on k. The prior overwhelms the data and drives the fit to K=0. Try imposing priors on one or both of the logk parameters or fit using the per tc secosw sesinw k basis.

sealauren commented 5 years ago

Thanks BJ!