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/4484#issuecomment-706937046,https://api.github.com/repos/pydata/xarray/issues/4484,706937046,MDEyOklzc3VlQ29tbWVudDcwNjkzNzA0Ng==,1277781,2020-10-12T07:36:34Z,2020-10-12T07:36:34Z,CONTRIBUTOR,"> If we're doing to do this, I would suggest that the right signature is `xarray.map(func, *datasets, **optional_kwargs)`, matching Python's builtin `map`.

What I'd like to ensure is a clean separation between the arguments of `xarray.map` and `func`. Map has three ""own"" parameters, like `func`, `datasets` and `keep_attrs`. By using the `**kwargs` approach we are excluding these parameter names from `func`. Not saying that is likely that anyone would apply a function with such parameter names. But not impossible either.
Also having a real  dict for keyword args (and maybe a list for positional arguments of `func`) is more explicit.

In my implementation the order of parameters is `datasets` and then `func` to match that of `Dataset.map` with the implicit `self`.
But probably `func` and then the `datasets` is more intuitive.
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-705078481,https://api.github.com/repos/pydata/xarray/issues/4484,705078481,MDEyOklzc3VlQ29tbWVudDcwNTA3ODQ4MQ==,1217238,2020-10-07T17:17:48Z,2020-10-07T17:17:48Z,MEMBER,"I think some version of `xarray.map` could indeed be pretty useful more generally. In particular, it could implement each of the ways to ""align"" variables between different datasets, e.g., should we use the intersection of the variables, or the union, inserting dummy variables with fill values? The `dataset_join` argument to `xarray.apply_ufunc` controls this behavior, but it would be nice to have a self-contained version of this.

One challenge for using this internally in xarray (vs. implementing things only on Dataset objects) is that the coordinates on the DataArray objects inside a Dataset can be redundant, so mapping over DataArrays may be less efficient, due to duplicate work on coordinates. In contrast, once everything is in Dataset objects, all the variables/coordinates are pre-aligned and de-deduplicated.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-705066436,https://api.github.com/repos/pydata/xarray/issues/4484,705066436,MDEyOklzc3VlQ29tbWVudDcwNTA2NjQzNg==,1277781,2020-10-07T16:56:04Z,2020-10-07T16:56:04Z,CONTRIBUTOR,">     * Are there many other cases outside of `xr.dot` which only operate on `DataArray`s? If not, we could update that function to take a `Dataset`

I think it would be a good idea to extend dot to Datasets. However a user may wish to map a custom DataArray function to Dataset.

>     * Maybe jumping ahead — are there functions where the result of `func(ds1, ds2)` shouldn't be that function mapped over the matching variables?

Not sure of the context of this. In the most general case one can certainly implement any function on ds1 and ds2. Or are you referring to the built-ins such as .dot?
","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-704647248,https://api.github.com/repos/pydata/xarray/issues/4484,704647248,MDEyOklzc3VlQ29tbWVudDcwNDY0NzI0OA==,2448579,2020-10-07T01:59:59Z,2020-10-07T01:59:59Z,MEMBER,"> Are there many other cases outside of xr.dot which only operate on DataArrays? If not, we could update that function to take a Dataset

I think we should do this. ","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-704632636,https://api.github.com/repos/pydata/xarray/issues/4484,704632636,MDEyOklzc3VlQ29tbWVudDcwNDYzMjYzNg==,5635139,2020-10-07T01:05:37Z,2020-10-07T01:05:37Z,MEMBER,"
> The motivating use case was that I wanted to compute the dot-product of two DataSets (=all of their matching variables).

Thanks, that's a good case. 

A couple of thoughts:
- Are there many other cases outside of `xr.dot` which only operate on `DataArray`s? If not, we could update that function to take a `Dataset`
- Along those lines, I wonder whether this becomes an underlying function — functions which currently operate only on `DataArray`s could have `Dataset` inputs run through this.
- NB: In many of the computation functions, the logic runs the other way (we define the `DataArray` function to be the `Dataset` operation on a single-variable `Dataset`); having a more consistent way of doing this could make extending functions between `DataArray`s & `Dataset`s easier.
- Maybe jumping ahead — are there functions where the result of `func(ds1, ds2)` shouldn't be that function mapped over the matching variables?

","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-704037491,https://api.github.com/repos/pydata/xarray/issues/4484,704037491,MDEyOklzc3VlQ29tbWVudDcwNDAzNzQ5MQ==,1277781,2020-10-06T05:32:04Z,2020-10-06T05:32:04Z,CONTRIBUTOR,"> Could I ask what the common use cases for this would be? If I understand correctly, running `map(x, y, lambda x: x + y)` is equivalent to `x + y`.

The motivating use case was that I wanted to compute the dot-product of two DataSets (=all of their matching variables).
But in general any other function which is not as simple as x + y could be used here.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-704033519,https://api.github.com/repos/pydata/xarray/issues/4484,704033519,MDEyOklzc3VlQ29tbWVudDcwNDAzMzUxOQ==,1217238,2020-10-06T05:19:44Z,2020-10-06T05:19:44Z,MEMBER,"I think this could make sense as a generalization of `Dataset.map`. I would indeed be interested to hear more about the specific use cases that motivated this, though.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-704031645,https://api.github.com/repos/pydata/xarray/issues/4484,704031645,MDEyOklzc3VlQ29tbWVudDcwNDAzMTY0NQ==,1217238,2020-10-06T05:13:29Z,2020-10-06T05:13:29Z,MEMBER,"If we're doing to do this, I would suggest that the right signature is `xarray.map(func, *datasets, **optional_kwargs)`, matching Python's builtin `map`.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-703962448,https://api.github.com/repos/pydata/xarray/issues/4484,703962448,MDEyOklzc3VlQ29tbWVudDcwMzk2MjQ0OA==,5635139,2020-10-06T00:37:46Z,2020-10-06T00:37:46Z,MEMBER,"Hi @kefirbandi , thanks for the PR!

Could I ask what the common use cases for this would be? If I understand correctly, running `map(x, y, lambda x: x + y)` is equivalent to `x + y`.","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717
https://github.com/pydata/xarray/pull/4484#issuecomment-703199290,https://api.github.com/repos/pydata/xarray/issues/4484,703199290,MDEyOklzc3VlQ29tbWVudDcwMzE5OTI5MA==,24736507,2020-10-04T04:11:38Z,2020-10-04T04:43:38Z,NONE,"Hello @kefirbandi! Thanks for updating this PR. We checked the lines you've touched for [PEP 8](https://www.python.org/dev/peps/pep-0008) issues, and found:











There are currently no PEP 8 issues detected in this Pull Request. Cheers! :beers: 

##### Comment last updated at 2020-10-04 04:43:38 UTC","{""total_count"": 0, ""+1"": 0, ""-1"": 0, ""laugh"": 0, ""hooray"": 0, ""confused"": 0, ""heart"": 0, ""rocket"": 0, ""eyes"": 0}",,714228717