## Cobaya: how can I change the range of variable?

Use of Cobaya. camb, CLASS, cosmomc, compilers, etc.
Zhu-Yao Wang
Posts: 15
Joined: September 16 2020
Affiliation: Northeastern University

### Cobaya: how can I change the range of variable?

Hi I'm now focusing on how Neff will affect . I tried to make the triangle plot but the range of Neff keeps in a very small region (2.9-3.3). But I want to expand this region to 0 to 6.
Here is my code and I tried to change scale but it doesn't work.

Code: Select all

nnu:
56     prior:
57       min: 0.05
58       max: 10
59     ref:
60       dist: norm
61       loc: 3.046
62       scale: 1
63     proposal: 0.05
Is there a way to change it wider range?

Natalie Hogg
Posts: 4
Joined: September 04 2020
Affiliation: ICG Portsmouth

### Re: Cobaya: how can I change the range of variable?

Do you mean you want to sample a larger range? If so, you need to change the min and max values of the prior in your .yaml file (though it looks like your prior is already covering the range 0 to 6).

If you've already run your chains and you want to simply change what is plotted by GetDist, you can include a file with the same name as your chain files, with the file type .ranges, in the same directory as your chain files. This file lists the minimum and maximum values for each parameter when plotted. It looks like this:

Code: Select all

omegabh2                  0.5000000E-02    0.1000000E+00
omegach2                  0.1000000E-02    0.9900000E+00
H0                        0.5500000E+02    0.8500000E+02
tau                       0.5800000E-01    0.5800000E-01
.ranges files are generated automatically by CosmoMC, but perhaps they are not generated by Cobaya. You don't need to specify a range for every parameter, so you could create such a file by hand, just giving the range for Neff. More info here under "Samples file format": https://getdist.readthedocs.io/en/latest/intro.html

Zhu-Yao Wang
Posts: 15
Joined: September 16 2020
Affiliation: Northeastern University

### Re: Cobaya: how can I change the range of variable?

Thanks Natalie. I meant to sample a larger range. I changed the prior but the result I got only cover a very small region. In the plot I got, the x axis range is 0-6 but the contours still lies within a small region(2.5-3.5). Is there a way to change the distribution? Thanks!