How do I add a new variable to dataset. (#3679)

* How do I add a new variable to dataset.

* Update doc/howdoi.rst

Improvement from dcherian

Co-Authored-By: Deepak Cherian <dcherian@users.noreply.github.com>

* Add cross-reference per suggestion.

* Fix cross-reference.

* Update doc/howdoi.rst

Suggestion from keewis

Co-Authored-By: keewis <keewis@users.noreply.github.com>

Co-authored-by: Deepak Cherian <dcherian@users.noreply.github.com>
Co-authored-by: keewis <keewis@users.noreply.github.com>

Author: 3 people

doc/data-structures.rst

@@ -353,6 +353,8 @@ setting) variables and attributes:
 This is particularly useful in an exploratory context, because you can
 tab-complete these variable names with tools like IPython.
 
+.. _dictionary_like_methods:
+
 Dictionary like methods
 ~~~~~~~~~~~~~~~~~~~~~~~
 

doc/howdoi.rst

@@ -11,6 +11,8 @@ How do I ...
 
    * - How do I...
      - Solution
+   * - add a DataArray to my dataset as a new variable
+     - ``my_dataset[varname] = my_dataArray`` or :py:meth:`Dataset.assign` (see also :ref:`dictionary_like_methods`)
    * - add variables from other datasets to my dataset
      - :py:meth:`Dataset.merge`
    * - add a new dimension and/or coordinate
@@ -57,3 +59,4 @@ How do I ...
      - ``obj.dt.ceil``, ``obj.dt.floor``, ``obj.dt.round``. See :ref:`dt_accessor` for more.
    * - make a mask that is ``True`` where an object contains any of the values in a array
      - :py:meth:`Dataset.isin`, :py:meth:`DataArray.isin`
+