html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/pull/2398#issuecomment-423167921,https://api.github.com/repos/pydata/xarray/issues/2398,423167921,MDEyOklzc3VlQ29tbWVudDQyMzE2NzkyMQ==,6815844,2018-09-20T12:40:16Z,2018-09-20T12:40:16Z,MEMBER,"Thanks, @rabernat for the review.

Added the limitation of this method to docs.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348
https://github.com/pydata/xarray/pull/2398#issuecomment-422973404,https://api.github.com/repos/pydata/xarray/issues/2398,422973404,MDEyOklzc3VlQ29tbWVudDQyMjk3MzQwNA==,6815844,2018-09-19T22:01:12Z,2018-09-19T22:01:12Z,MEMBER,"Thanks all. Updated.

Thanks, @spencerkclark 

> Eventually it would be nice if this worked on DataArrays with cftime.datetime coordinates; I think it would be relatively straightforward to modify to_numeric to enable it (we could probably enable it for interp at the same time), but I can take care of that later if you'd like.

Thanks. I added this function for something like this extension, though I do not yet fully follow your cftime update. It would be super nice if you could take care of this after merge.

@shoyer ,

> we might want to include an option for periodic boundary conditions 

Agreed. This option is nice not only `differentiate` but also `interp` and [`rolling`](#2011).
I think we can add a common logic to take care of them.

@fmaussion 

> See also #1288 : integrate is the next on my list ;) - I can try to give it a go if @fujiisoup doesn't want to do it himself

Thanks. 
Actually, I am now moving to another nation and would not have enough time in a few weeks.
I will appreciate if you could take care of this.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348
https://github.com/pydata/xarray/pull/2398#issuecomment-422639302,https://api.github.com/repos/pydata/xarray/issues/2398,422639302,MDEyOklzc3VlQ29tbWVudDQyMjYzOTMwMg==,6815844,2018-09-19T03:35:51Z,2018-09-19T03:35:51Z,MEMBER,I think it's ready :),"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348
https://github.com/pydata/xarray/pull/2398#issuecomment-420474101,https://api.github.com/repos/pydata/xarray/issues/2398,420474101,MDEyOklzc3VlQ29tbWVudDQyMDQ3NDEwMQ==,6815844,2018-09-12T00:49:23Z,2018-09-12T00:49:23Z,MEMBER,"Thanks, @dopplershift .

> Aren't you taking differences of values and dividing by differences between the matching coordinates?

Yes, correct. But if we have closer data points, then the estimate of the gradient becomes more precise. Sorting the array according to the coordinate provides the closest points, resulting in the most precise estimate of the gradient.

But I also think users can do it manually before taking the gradient. 

","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348
https://github.com/pydata/xarray/pull/2398#issuecomment-420458057,https://api.github.com/repos/pydata/xarray/issues/2398,420458057,MDEyOklzc3VlQ29tbWVudDQyMDQ1ODA1Nw==,6815844,2018-09-11T23:18:17Z,2018-09-11T23:18:17Z,MEMBER,any thoughts for this?,"{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348
https://github.com/pydata/xarray/pull/2398#issuecomment-418541019,https://api.github.com/repos/pydata/xarray/issues/2398,418541019,MDEyOklzc3VlQ29tbWVudDQxODU0MTAxOQ==,6815844,2018-09-04T22:41:41Z,2018-09-04T22:41:41Z,MEMBER,"> I wonder if we should consider calling this xarray.differentiate instead of xarray.gradient. I think the NumPy function is poorly named for differentiating along a single axis at once.

Agreed. Differentiate is nicer.

Some other api questions arised during the implementation
+ Do we support `differentiate` for `Dataset`? In that case, what should we do for the variables that are independent from the target coordinate?
I thought 'keep them as is' is intuitive (and I implemented so), but mathematically, they should be zero.

+ Do we need to sort the array before computing `differentiate`? `np.gradient` implicitly assumes the array is sorted (but do nothing about this).","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,356698348