Add io/plink docs

Author: ravwojdyla

docs/api.rst

@@ -1,11 +1,26 @@
-.. currentmodule:: sgkit
-
 #############
 API reference
 #############
 
 This page provides an auto-generated summary of sgkits's API.
 
+IO/imports
+==========
+
+.. currentmodule:: sgkit.io.plink
+.. autosummary::
+   :toctree: generated/
+
+    read_plink
+
+.. currentmodule:: sgkit
+.. autosummary::
+   :toctree: generated/
+
+    read_vcfzarr
+
+.. currentmodule:: sgkit
+
 Creating a dataset
 ==================
 
@@ -14,7 +29,6 @@ Creating a dataset
 
    create_genotype_call_dataset
    create_genotype_dosage_dataset
-   read_vcfzarr
 
 Methods
 =======

docs/index.rst

@@ -2,12 +2,13 @@ sgkit: Statistical genetics toolkit in Python
 =============================================
 
 .. toctree::
-   :maxdepth: 2
-   :caption: Contents:
+    :maxdepth: 2
+    :caption: Contents:
 
-   api
-   usage
-   contributing
+    api
+    usage
+    io
+    contributing
 
 
 Indices and tables

docs/io.rst

@@ -0,0 +1,16 @@
+.. _io:
+
+IOs
+===
+
+PLINK
+-----
+
+The :func:`sgkit.io.plink.read_plink` loads a single PLINK dataset as Dask
+arrays within an `xr.Dataset` from bed, bim, and fam files.
+
+PLINK IO support is an "extra" feature within sgkit and requires additional
+dependencies. To install sgkit with PLINK support using pip::
+
+    $ pip install git+https://github.com/pystatgen/sgkit#egg=sgkit[plink]
+