Negative chi^2 from Commander
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Björn Sörgel
- Posts: 13
- Joined: April 05 2013
- Affiliation: Institute of Astronomy/Kavli Institute for Cosmology Cambridge
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by Björn Sörgel » October 22 2013
Dear all,
when I run with
feedback=3, the following LnLike and Chi2 are printed for the individual datasets:
Code: Select all
Calling CAMB
CAMB done
lowlike_v222.clik lnlike = 1007.28444991537
DR7 BAO likelihood = 1.91087739414207
6DF BAO likelihood = 1.449826393350034E-002
DR9 BAO likelihood = 5.291717134685368E-002
commander_v4.1_lm49.clik lnlike = -3.74495218656174
CAMspec_v6.2TN_2013_02_26_dist.clik lnlike = 4192.16885357843
1007.284 2014.569 CMB: lowlike_v222.clik
1.911 3.822 BAO: DR7
0.014 0.029 BAO: 6DF
0.053 0.106 BAO: DR9
-3.745 -7.490 CMB: commander_v4.1_lm49.clik
4192.169 8384.338 CMB: CAMspec_v6.2TN_2013_02_26_dist.clik
Why is there a negative chi2 from commander? And secondly, isn't the BAO chi2 very low?. I first discovered this in a modified Jun2013 version, but I could reproduce it with a vanilla Oct2013 one.
Cheers,
Björn
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Antony Lewis
- Posts: 1944
- Joined: September 23 2004
- Affiliation: University of Sussex
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Contact:
Post
by Antony Lewis » October 22 2013
The normalization of the likelihoods is arbitrary (constant offsets in the log like don't matter); they could have added a constant offset to the commander likelihood to make it look like a \chi^2 but didn't.
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Björn Sörgel
- Posts: 13
- Joined: April 05 2013
- Affiliation: Institute of Astronomy/Kavli Institute for Cosmology Cambridge
Post
by Björn Sörgel » October 22 2013
Dear Antony,
thanks for the quick reply. "Problem" solved.
Cheers,
Björn
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Luke Hart
- Posts: 70
- Joined: July 13 2015
- Affiliation: University of Manchester
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by Luke Hart » August 02 2017
Antony Lewis wrote:The normalization of the likelihoods is arbitrary (constant offsets in the log like don't matter); they could have added a constant offset to the commander likelihood to make it look like a \chi^2 but didn't.
Antony, it seems that if you try and run GetDistGUI.py with this dataset, it won't let you view the .margestats or the Parameter tables due to the negative chi2 from commander? Anyway you can think of getting around this??
Luke
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Antony Lewis
- Posts: 1944
- Joined: September 23 2004
- Affiliation: University of Sussex
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Contact:
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by Antony Lewis » August 02 2017
You need to edit the .ranges file for the chain, and remove the 0 N range for chi2_xxx where xxx is the likelihood.
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Luke Hart
- Posts: 70
- Joined: July 13 2015
- Affiliation: University of Manchester
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by Luke Hart » August 02 2017
Fantastic thank you :)