Minor bugfix to account for only 12 columns in weight file

[ammcpherson]

Hello,

I believe that at one point the weights files had 13 columns, and at some point this changed to only 12. I have updated the parse_statistics function to read in the proper columns for static time shifts.

Thanks,
Amanda

[rmodrak]

Can we generalize the weight file format and reader to accommodate different existing conventions?

Following discussion with others in 2020, I started using a 13 column weight file (introduced by Celso?) and still continue to use it

[ammcpherson]

If the order never changes, we could do something akin to:

statics[_code]['surface_wave_Z'] = float(row[-2])
statics[_code]['surface_wave_R'] = float(row[-2])
statics[_code]['surface_wave_T'] = float(row[-1])

But I think that if we are encouraging people to use PySEP to download data, this will always fall victim to needing to be kept up to date with whatever changes happen there.

[ammcpherson]

I have two more thoughts regarding this:

1. The default data used in all the examples currently has a weights file with 12 columns, and has a header line describing what each column is. However, weights files written out by PySEP do not have this header.
2. It is far easier for experienced users such as you and I, albeit still frustrating, to adapt our scripts and workflows to changes like these than new users.

I think that the long term solution is to ask for PySEP to write out a weights file with a descriptive header, such that we can write a function to read it in as a pandas DataFrame with column names, which would be about as generalized as I think it could be.

In the short term though, I think that we need to have this fixed for new users.