Convert FAR to units of Hz when dumping to XML

[spxiwh]

This is a small patch to convert the units of combined_far in our XML coinc output files to Hz. Note that our conversion between seconds and years is slightly unclear as described in #217, this should be fixed.

[tdent]

Please use LAL SI Julian year Ian .. and check the order of magnitude is correct by running the patched code on the ER7 events. Are you sure you should be multiplying by the LAL conversion factor rather than dividing?

[spxiwh]

Hi Tom,

I have updated the patch to divide by the rescaling factor, which now gives sane values (ie. most significant event is 9.78E-7). I agree that we should use LAL SI Julian year, but if I use a different value from what Alex has when computing the FAR then this will not be valid.

Cheers
Ian

[tdent]

.. Then make the change in both codes in the same request, even preferably in the same commit, so that there won't be a state of the code where there is an inconsistency. Then we can close #217.

The FAR calculation works in seconds anyway, it's only converted for output / storage / display purposes.

[ahnitz]

Thanks for fixing this. If we can do the change all at once to use the correct number that would be best.

[spxiwh]

Okay I've converted the patch to use lal.YRJUL_SI as requested and also changed this in the HDF FAR codes.

I'm assigning this now to Alex to check that there isn't anywhere else in the HDF code where this number is hardcoded? Tom, please speak up if you are not happy with this now.

[tdent]

Thanks Ian. I have checked the lal.YRJUL_SI constant is a python float, so there won't be integer division issues (which might have occurred since the Julian year is an exact number of seconds).
Could you please roll all 3 commits together with git rebase --interactive and update the branch via push -f, that would make the history a lot cleaner/more comprehensible and avoid buggy intermediate states.

[spxiwh]

This is now rebased into a single commit

[ahnitz]

The commits fix the FAR assignment codes in the right place, so I'm happy for this to merge.