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
526243198,MDU6SXNzdWU1MjYyNDMxOTg=,3556,doc\environment.yml not found,45787861,closed,0,,,6,2019-11-20T22:07:36Z,2019-11-20T22:29:46Z,2019-11-20T22:29:46Z,NONE,,,,"#### MCVE Code Sample
<!-- In order for the maintainers to efficiently understand and prioritize issues, we ask you post a ""Minimal, Complete and Verifiable Example"" (MCVE): http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports -->

I would like to contribute to the xarray documentation.

Therefore, I tried to install the `xarray-docs` environment as described in the [contributing guidelines](http://xarray.pydata.org/en/stable/contributing.html#requirements):
```bash
# Create and activate the docs environment
conda env create -f doc/environment.yml
```

#### Expected Output

Creates the `xarray-docs` environment such that it can be activated.

#### Problem Description
<!-- this should explain why the current behavior is a problem and why the expected output is a better solution -->
```bash
EnvironmentFileNotFound: '...\xarray\doc\environment.yml' file not found
```

#### Output of ``xr.show_versions()``

**xarray: 0.14.1+11.ga4d04466**

<details>
INSTALLED VERSIONS
------------------
commit: None
python: 3.7.5 (default, Oct 31 2019, 15:18:51) [MSC v.1916 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 142 Stepping 10, GenuineIntel
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8
LOCALE: None.None
libhdf5: 1.10.4
libnetcdf: 4.6.1

xarray: 0.14.1+11.ga4d04466
pandas: 0.25.3
numpy: 1.17.3
scipy: 1.3.1
netCDF4: 1.4.2
pydap: None
h5netcdf: None
h5py: None
Nio: None
zarr: None
cftime: 1.0.4.2
nc_time_axis: None
PseudoNetCDF: None
rasterio: None
cfgrib: None
iris: None
bottleneck: None
dask: None
distributed: None
matplotlib: 3.1.1
cartopy: None
seaborn: None
numbagg: None
setuptools: 41.6.0.post20191030
pip: 19.3.1
conda: None
pytest: 5.2.4
IPython: 7.9.0
sphinx: None
</details>
","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3556/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue
525642358,MDU6SXNzdWU1MjU2NDIzNTg=,3549,Creating conda environment as described in the contributing guidelines gives ResolvePackageNotFound error,45787861,closed,0,,,2,2019-11-20T08:12:18Z,2019-11-20T10:12:57Z,2019-11-20T09:47:57Z,NONE,,,,"#### MCVE Code Sample
<!-- In order for the maintainers to efficiently understand and prioritize issues, we ask you post a ""Minimal, Complete and Verifiable Example"" (MCVE): http://matthewrocklin.com/blog/work/2018/02/28/minimal-bug-reports -->

Following the [contributing to xarray guidelines](http://xarray.pydata.org/en/stable/contributing.html#creating-a-python-environment) I tried to create the xarray-test environment as follows:
```bash
# Create and activate the build environment
conda env create -f ci/requirements/py36.yml
```

#### Expected Output
Creates conda environment, such that `conda activate xarray-tests` can be used to activate it.

#### Problem Description
<!-- this should explain why the current behavior is a problem and why the expected output is a better solution -->
The creation of the conda environment fails, indicating `ResolvePackageNotFound ` error:
```bash
Collecting package metadata: done
Solving environment: failed

ResolvePackageNotFound:
  - pynio
  - cdms2
```

After some searching I tried to first create the conda environment and subsequently updating it

```bash
conda env update -f ci/requirements/py36.yml
```
but this resulted in the same error:

```bash
Collecting package metadata: done
Solving environment: failed

ResolvePackageNotFound:
  - pynio
  - cdms2
```


#### Output of ``xr.show_versions()``
Doesn't make sense for this issue, does it?","{""url"": ""https://api.github.com/repos/pydata/xarray/issues/3549/reactions"", ""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,completed,13221727,issue