issue_comments

Table actions

6 rows where author_association = "MEMBER" and issue = 217385961 sorted by updated_at descending

✎ View and edit SQL

This data as json, CSV (advanced)

Suggested facets: reactions, created_at (date), updated_at (date)

user 2

issue 1

  • Shape preserving `diff` via new keywords · 6 ✖

author_association 1

  • MEMBER · 6 ✖
id html_url issue_url node_id user created_at updated_at ▲ author_association body reactions performed_via_github_app issue
418161473 https://github.com/pydata/xarray/issues/1332#issuecomment-418161473 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDQxODE2MTQ3Mw== shoyer 1217238 2018-09-03T16:56:26Z 2018-09-03T16:56:26Z MEMBER

I agree that we should have a "middle" or "centered" option for xarray.diff. On Mon, Sep 3, 2018 at 9:14 AM T. Chor notifications@github.com wrote:

I'm not sure where we stand on this issue, but I think since numpy.gradient already exists, it makes more sense to wrap that function for the sake of simplicity instead of making xr.diff differ from the original premise of np.diff.

On the same topic, it bothers me that xr.diff only accepts "upper" and "lower" arguments for the label. The most obvious (and useful) value in my opinion would be "middle", which would correspond to a centered finite differences. Is there any special reason why that option isn't there?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/pydata/xarray/issues/1332#issuecomment-418154705, or mute the thread https://github.com/notifications/unsubscribe-auth/ABKS1pWdcdpNtLK18J8v6z8AimuBryT_ks5uXVV3gaJpZM4Mq3x- . 

{
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961
289859704 https://github.com/pydata/xarray/issues/1332#issuecomment-289859704 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDI4OTg1OTcwNA== rabernat 1197350 2017-03-28T18:21:17Z 2017-03-28T18:21:17Z MEMBER

@rabernat, do you think that the proposed keyword additions should be included in xarray or not?

If you are going to have diff return a same-length array, then the keywords should allow the user to specify the boundary condition, e.g. extend, reflect, periodic, blank, etc. I agree this would be useful to have in xarray.

I also agree we should copy numpy wherever possible.

 
{
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961
289858583 https://github.com/pydata/xarray/issues/1332#issuecomment-289858583 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDI4OTg1ODU4Mw== shoyer 1217238 2017-03-28T18:17:18Z 2017-03-28T18:17:18Z MEMBER

As I mentioned in #1288, I think basic functionality like integrate and gradient is totally within appropriate scope for xarray.

I recall now that people have requested similar functionality for numpy.diff: https://github.com/numpy/numpy/issues/8132. It would be nice to resolve this upstream in NumPy first (e.g., with https://github.com/numpy/numpy/pull/8206), and then simply copy the API design in xarray.

 
{
    "total_count": 2,
    "+1": 2,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961
289839737 https://github.com/pydata/xarray/issues/1332#issuecomment-289839737 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDI4OTgzOTczNw== rabernat 1197350 2017-03-28T17:13:00Z 2017-03-28T17:13:00Z MEMBER

It is just super inconvenient to do array resizing following the diff of a time vector to get timesteps, but maybe this use case is too niche to be useful for the community.

Maybe for the xarray community, but not the xgcm community ;) We definitely want round-trip-compatibly diff and cumsum operations (see xgcm/xgcm#49, which is very close to implemented)

 
{
    "total_count": 1,
    "+1": 1,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961
289790359 https://github.com/pydata/xarray/issues/1332#issuecomment-289790359 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDI4OTc5MDM1OQ== rabernat 1197350 2017-03-28T14:35:41Z 2017-03-28T14:35:41Z MEMBER

FYI @pwolfram, if you are interested in more "grid-aware" finite differencing, you might have a look at xgcm. We are working on it again and have implemented some basic difference and interpolation operators: http://xgcm.readthedocs.io/en/latest/grids.html#grid-objects 

{
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961
289671227 https://github.com/pydata/xarray/issues/1332#issuecomment-289671227 https://api.github.com/repos/pydata/xarray/issues/1332 MDEyOklzc3VlQ29tbWVudDI4OTY3MTIyNw== shoyer 1217238 2017-03-28T05:56:57Z 2017-03-28T05:56:57Z MEMBER

Would it fill the same need to add a wrapped version of np.gradient, which already works similarly to diff but preserves input shape?

 
{
    "total_count": 0,
    "+1": 0,
    "-1": 0,
    "laugh": 0,
    "hooray": 0,
    "confused": 0,
    "heart": 0,
    "rocket": 0,
    "eyes": 0
}
   Shape preserving `diff` via new keywords 217385961

Advanced export

JSON shape: default, array, newline-delimited, object

CSV options: 

CREATE TABLE [issue_comments] (
   [html_url] TEXT,
   [issue_url] TEXT,
   [id] INTEGER PRIMARY KEY,
   [node_id] TEXT,
   [user] INTEGER REFERENCES [users]([id]),
   [created_at] TEXT,
   [updated_at] TEXT,
   [author_association] TEXT,
   [body] TEXT,
   [reactions] TEXT,
   [performed_via_github_app] TEXT,
   [issue] INTEGER REFERENCES [issues]([id])
);
CREATE INDEX [idx_issue_comments_issue]
    ON [issue_comments] ([issue]);
CREATE INDEX [idx_issue_comments_user]
    ON [issue_comments] ([user]);