id,node_id,number,title,user,state,locked,assignee,milestone,comments,created_at,updated_at,closed_at,author_association,active_lock_reason,draft,pull_request,body,reactions,performed_via_github_app,state_reason,repo,type
525685973,MDExOlB1bGxSZXF1ZXN0MzQzMjU4Njg2,3550,cov() and corr() - finalization,45787861,closed,0,,,52,2019-11-20T09:40:54Z,2020-05-25T16:57:05Z,2020-05-25T16:57:04Z,NONE,,0,pydata/xarray/pulls/3550,"<!-- Feel free to remove check-list items aren't relevant to your change -->

Dear maintainers, 

this is my first PR and contribution to xarray. I have read the [contributing guidelines](xarray.pydata.org/en/stable/contributing.html) and did my best to conform to your [code of conduct](). However, I would be happy if you have a closer look whether everything is correct and give feedback for improvement!

As I don't have push access to @hrishikeshac's fork, I created this PR to add the final changes for PR #2652.

 - [x] Closes #2652
 - [x] Tests had been added in #2652
 - [ ] Passes `black . && mypy . && flake8`
   - [x] black
   - [x] flake8
   - [ ] mypy
 - [x] Fully documented, including `whats-new.rst` for all changes and `api.rst` for new API
   - [x]  `whats-new.rst`
   - [x] `api.rst`
- [x] example notebook for usage of `corr()` and `cov()`
  - [x] where and how to write the examples?
  - [x] covariance
  - [x] correlation
- [x] moved implementation of cov() and corr() to computation
- [x] add test_cov()
- [x] remove da.cov and da.corr","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3550/reactions"", ""total_count"": 1, ""+1"": 1, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,,13221727,pull