grdmath SUB operator

[arleaman]

grdmath SUB operator

I would like to use this feature to calculate residuals by finding the difference between two grid files.

Are you willing to help implement and maintain this feature? Yes, with guidance

[welcome]

👋 Thanks for opening your first issue here! Please make sure you filled out the template with as much detail as possible. You might also want to take a look at our contributing guidelines and code of conduct.

[weiji14]

Hi @arleaman, just need a bit more information on what your 'grids' are. Are they NetCDF files, xarray.DataArray/xarray.Dataset objects, or something else? This will help us to advice you a bit better.

About calculating residuals (using SUB), I would recommend doing it directly in xarray (see http://xarray.pydata.org/en/v0.16.2/computation.html#basic-array-math) using the minus '-' operator if possible, assuming that you are already familiar with xarray. Not to say we can't wrap a grdmath function in PyGMT, but the reverse polish notation of grdmath will make implementing this a bit tricky (though you are welcome to try).

[arleaman]

Thanks @weiji14 - I am using NetCDF files for my grids and will look into performing calculations in xarray.