Why spacing information is added as a new coordinate

[lanougue]

When computing xrft.dft over dimension "x", a "freq_x_spacing" is added in the output as a new coordinates of dimension "1".
This new coord is disturbing since its not really a new dimension/coordinate.
Could it be better option to add this spacing information in output attributes instead of coordinates ?

[rabernat]

Could it be better option to add this spacing information in output attributes instead of coordinates ?

Yes, that would be fine with me! This was a somewhat random choice early on.

[lanougue]

I think this spacing parameter should be a coordinate's attribute instead of an attribute of the dft itself.
The reason is that attributes are easily removed with simple operation such as
A = xr.dft(..., dim='x')
B = 3*A
B have lost spacing attributes.

However, if spacing is an attribute of freq_x in A, it will be kept in B. It will be removed only if some operation is realized on the freq_x coordinate vector (which is almost never happening).
The user can of course use xr.set_options(keep_attrs=True) but I don't think it is desirable.
And, spacing is, by definition, a coordinate attributes.
What do you think ?

[lanougue]

I opened PR #126 to discuss about that

[lanougue]

solved in PR #126