monotonically increasing check should be ">="

[greglucas]

A monotonic function can have values that are equal to each other
https://en.wikipedia.org/wiki/Monotonic_function

so I believe this should be >=

cdflib/cdflib/xarray/xarray_to_cdf.py

Line 471 in 88ba11e

return np.all(epoch_data[1:] > epoch_data[:-1])

It does seem like there is some ambiguity about whether monotonically increasing includes the equal sign or not. I couldn't figure out which definition ISTP compliance would want. "strictly increasing" would be how I would interpret the code currently.

[ericthewizard]

A time series should be increasing in time (with no duplicate times); "strictly increasing" is probably better wording.

There's definitely some code out there (e.g., in IDL SPEDAS) that uses this assumption for performance reasons (I vaguely remember coming across it in the past).