Dear all,
I have a question related to the information displayed in the tables generated by GetDist. I am analysing with GetDist some chains produced using Cobaya. I would like to know what the [math] value shown inside the parenthesis, besides the chi2 value, represents.
For illustration, I add below a piece of code. Thanks in advance for your replies.
Regards,
Claudia
info = yaml_load_file(yaml_file)
from getdist.mcsamples import MCSamples
#Load samples from chain:
gd_sample = loadMCSamples(os.path.abspath(info["output"]), settings={'ignore_rows':0.3})
gd_sample.getTable().tableTex()
Tables generated by GetDist from MCMC chains produced with Cobaya code
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- Posts: 2
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- Affiliation: Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata / CONICET
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Re: Tables generated by GetDist from MCMC chains produced with Cobaya code
It's a measure of the effective degrees of freedom, defined by sigma^2/2 where sigma^2 is the variance of the chi2 value.
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- Posts: 2
- Joined: October 14 2006
- Affiliation: Facultad de Ciencias Astronómicas y Geofísicas, Universidad Nacional de La Plata / CONICET
Re: Tables generated by GetDist from MCMC chains produced with Cobaya code
Thank you, Antony,
I have noticed that this number ([math]) changes in different runs, even if I repeat the MCMC with the same setting (priors, reference PDF, proposal...) Also it changes if I change the reference PDF (despite I run 8 chains, and the covariance matrix of the parameters is updated on the flight).
Is there a way to use this ([math]) to decide if the posterior PDFs for the parameters are fine? Should it be close to the chi2 value? What can I conclude if this is larger or smaller than the chi2 value?
Thanks again for your comments.
Claudia
I have noticed that this number ([math]) changes in different runs, even if I repeat the MCMC with the same setting (priors, reference PDF, proposal...) Also it changes if I change the reference PDF (despite I run 8 chains, and the covariance matrix of the parameters is updated on the flight).
Is there a way to use this ([math]) to decide if the posterior PDFs for the parameters are fine? Should it be close to the chi2 value? What can I conclude if this is larger or smaller than the chi2 value?
Thanks again for your comments.
Claudia