Update to readme

Author: jeromekelleher

README.md

@@ -1,25 +1,82 @@
 # sc2ts
-Infer a succinct tree sequence from SARS-COV-2 variation data
 
+Sc2ts stands for "SARS-CoV-2 to tree sequence" (pronounced "scoots" optionally)
+and consists of
 
-If you are interested in helping to develop sc2ts or would like to
-work with the inferred ARGS, please get in touch.
+1. A method fo infer Ancestral Recombination Graphs (ARGs) from SARS-CoV-2
+data at pandemic scale
+2. A lightweight wrapper around [tskit Python APIs](https://tskit.dev/tskit/docs/stable/python-api.html) specialised for the output of sc2ts which enables efficient node metadata
+access.
+3. A lightweight wrapper around [Zarr Python](https://zarr.dev) which enables
+convenient and efficient access to the full Viridian dataset (alignments and metadata)
+in a single file using [VCF Zarr specification](https://doi.org/10.1093/gigascience/giaf049).
 
+Please see the [preprint](https://www.biorxiv.org/content/10.1101/2023.06.08.544212v2)
+for details.
 
-Then, download the ARG in tszip format from
-[Zenodo](https://zenodo.org/records/17558489/):
+## Installation
+
+Install sc2ts from PyPI:
+
+```
+python -m pip install sc2ts
+```
+
+This installs the minimum requirement to enable the
+[ARG analysis](#ARG-analysis-API) and [Dataset](#Dataset-API)s.
+To run [inference](#inference), you must install some extra
+dependencies using the 'inference' optional extra:
+
+```
+python -m pip install sc2ts[inference]
+```
+
+## ARG analysis API
+
+The sc2ts API provides two convenience functions to compute summary
+dataframes for the nodes and mutations in a sc2ts-output ARG.
+
+To see some examples, first download the sc2ts inferred ARG
+from [Zenodo](https://zenodo.org/records/17558489/):
 
 ```
 curl -O https://zenodo.org/records/17558489/files/sc2ts_viridian_v1.2.trees.tsz
 ```
 
+We can then use these like
 
+```python
+import sc2ts
+import tszip
 
-## Installation
+ts = tszip.load("sc2ts_viridian_v1.2.trees.tsz")
+
+df_node = sc2ts.node_data(ts)
+df_mutation = sc2ts.mutation_data(ts)
+```
+
+See the [live demo](https://tskit.dev/explore/lab/index.html?path=sc2ts.ipynb)
+for a browser based interactive demo of using these dataframes for
+real-time pandemic-scale analysis.
+
+## Dataset API
 
-** TODO document local install **
+Sc2ts also provides a convenient API for accessing large-scale
+alignments and metadata stored in
+[VCF Zarr](https://doi.org/10.1093/gigascience/giaf049) format.
 
-## Inference workflow
+Resources:
+
+- See this [notebook](https://github.com/jeromekelleher/sc2ts-paper/blob/main/notebooks/example_data_processing.ipynb)
+for an example in which we access the data variant-by-variant and
+which explains the low-level data encoding
+- See the [VCF Zarr publication](https://doi.org/10.1093/gigascience/giaf049)
+for more details on and benchmarks on this dataset.
+
+
+**TODO** Add some references to API documentation
+
+## Inference
 
 ### Command line inference
 
@@ -163,6 +220,7 @@ the existing ``strain`` field is renamed to ``sample_id``
 field (extracted from the Viridian metadata) is renamed to ``pango``.
 
 We can then use the analysis APIs on this file:
+
 ```python
 import sc2ts
 import tskit