Xarray flexible indexes blog post

src/posts/flexible-indexes/index.md

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+---
+title: 'Xarray indexes: unleash the power of coordinates'
+date: '2023-08-07'
+authors:
+  - name: Benoît Bovy
+    github: benbovy
+summary: 'It is now possible to take full advantage of coordinate data via Xarray explicit and flexible indexes'
+---
+
+_TLDR: Xarray has been through a major refactoring of its internals that makes coordinate-based data selection and alignment (almost) fully customizable, via built-in and/or 3rd party indexes. It also addresses a good amount of long-standing issues with "dimension coordinates" implicitly backed by pandas (multi-)indexes._
+
+## Introduction
+
+[link to Joe's CZI blog post]
+
+## The concept of "dimension coordinate" and its shortcomings
+
+Some datasets could not be loaded with Xarray (dimension name and coordinate with same name but different dimensions)
+
+Complicated workarounds (swap_dims, etc.)
+
+Limited and/or challenging for data cubes representing arbitrary grids (curvilinear grids, unstructured meshes, etc.).
+
+## Better index vs. coordinate separation
+
+Refactor index logic in `Index` classes. More easily maintainable. May help Pandas become optional dependency in the future? (cf. Xarray-lite).
+
+Also allowed to solve lots of issues with multi-indexes, for which each level has now its own real coordinate.
+
+Dataset / DataArray section has now an "indexes" section.
+
+## Selection using non-dimension, 1-d coordinates
+
+Set an index for non-dimension coordinates! (No more swap_dims anymore or coordinate renaming)
+
+```python
+ds.set_xindex(“non_dim_coord”).sel(non_dim_coord=“something”)
+```
+
+## Alternatives to pandas.Index
+
+E.g., Numpy index (much faster to build, much more expensive to query), Geometry index (xvec)
+
+Out-of-core index, etc.
+
+...or no index at all! (Create dataset with no default index, `drop_indexes`)
+
+## Create custom indexes from arbitrary coordinates and dimensions
+
+Not limited to 1-dimensional coordinates, even more flexible!
+
+RasterIndex, FunctionalIndex, etc.
+
+See xarray discussion for examples
+
+## What’s next
+
+Still unfinished [link: indexes next steps GH issue], extension entry points, etc.
+
+## Acknowledgments
+
+CZI, Xarray core developers, etc.