issue_comments: 422083146

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https://github.com/pydata/xarray/issues/1613#issuecomment-422083146 https://api.github.com/repos/pydata/xarray/issues/1613 422083146 MDEyOklzc3VlQ29tbWVudDQyMjA4MzE0Ng== 98330 2018-09-17T16:31:51Z 2018-09-17T16:31:51Z NONE

Consider using index.is_monotonic_ascending and index.is_monotonic_descending instead of subtracting the first few values -- those are exactly the checks that pandas uses.

Thanks, that's nicer, will do. And thanks for digging up the background/rationales.

(1)Integer slicing by position and by label with positive integers should work the same for an index with values given by range(N).

This I don't think I agree with. Slicing by position and by label are semantically very different operations.

(2) is correct, but irrelevant to label-based indexing.

(3) yes, agree that's a mistake

(4) indeed

(5) I'd say that it's in practice less important, because users normally won't do slice(high, low), but for consistency I agree that there should be symmetry in behaviour. Making slice(high, low) return the same as slice(low, high) on a monotonic increasing index seems reasonable.

Additionally: arguably monotonicity should not be required. When one uses labels, the semantics are clear without monotonicity. This doesn't have a position-based equivalent.

 
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