Add docs for individual parents

docs/data-model.rst

@@ -259,6 +259,7 @@ Column              Type                Description
 ================    ==============      ===========
 flags               uint32              Bitwise flags.
 location            double              Location in arbitrary dimensions
+parents             int32               Ids of parent individuals
 metadata            binary              Individual :ref:`sec_metadata_definition`
 ================    ==============      ===========
 
@@ -281,6 +282,10 @@ so different individuals can have locations with different dimensions (i.e.,
 one individual may have location ``[]`` and another ``[0, 1, 0]``. This could
 therefore be used to store other quantities (e.g., phenotype).
 
+The ``parents`` column stores the ids of other individuals that are the parents of
+an individual. This column is :ref:`ragged <sec_encoding_ragged_columns>` such that an
+individual can have any number of parents.
+
 The ``metadata`` column provides a location for client code to store
 information about each individual. See the :ref:`sec_metadata_definition` section for
 more details on how metadata columns should be used.
@@ -1078,26 +1083,26 @@ Individual text format
 ======================
 
 The individual text format must contain a ``flags`` column.
-Optionally, there may also be a ``location`` and
+Optionally, there may also be ``location``, ``parents`` and
 ``metadata`` columns. See the :ref:`individual table definitions
 <sec_individual_table_definition>` for details on these columns.
 
 Note that there are currently no globally defined ``flags``, but the column
 is still required; a value of ``0`` means that there are no flags set.
 
-The ``location`` column should be a sequence of comma-separated numeric
+The ``location`` and ``parents`` columns should be a sequence of comma-separated numeric
 values. They do not all have to be the same length.
 
 An example individual table::
 
-    flags   location
-    0           0.5,1.2
-    0           1.0,3.4
+    flags       location     parents
+    0           0.5,1.2      -1, -1
+    0           1.0,3.4      0, -1
     0
     0           1.2
-    0           3.5,6.3
-    0           0.5,0.5
-    0           0.5
+    0           3.5,6.3      1,2
+    0           0.5,0.5      3,4
+    0           0.5          -1,-1
     0           0.7,0.6,0.0
     0           0.5,0.0
 

python/tskit/tables.py

@@ -457,6 +457,12 @@ class IndividualTable(BaseTable, MetadataMixin):
     :ivar location_offset: The array of offsets into the location column. See
         :ref:`sec_encoding_ragged_columns` for more details.
     :vartype location_offset: numpy.ndarray, dtype=np.uint32
+    :ivar parents: The flattened array of parent individual ids. See
+        :ref:`sec_encoding_ragged_columns` for more details.
+    :vartype parents: numpy.ndarray, dtype=np.int32
+    :ivar parents_offset: The array of offsets into the parents column. See
+        :ref:`sec_encoding_ragged_columns` for more details.
+    :vartype parents_offset: numpy.ndarray, dtype=np.uint32
     :ivar metadata: The flattened array of binary metadata values. See
         :ref:`sec_tables_api_binary_columns` for more details.
     :vartype metadata: numpy.ndarray, dtype=np.int8
@@ -522,6 +528,8 @@ def add_row(self, flags=0, location=None, parents=None, metadata=None):
         :param array-like location: A list of numeric values or one-dimensional numpy
             array describing the location of this individual. If not specified
             or None, a zero-dimensional location is stored.
+        :param array-like parents: A list or array of ids of parent individuals. If not
+            specified an empty array is stored.
         :param object metadata: Any object that is valid metadata for the table's schema.
             Defaults to the default metadata value for the table's schema. This is
             typically ``{}``. For no schema, ``None``.
@@ -555,6 +563,8 @@ def set_columns(
         the table will contain.
         The ``location`` and ``location_offset`` parameters must be supplied
         together, and meet the requirements for :ref:`sec_encoding_ragged_columns`.
+        The ``parents`` and ``parents_offset`` parameters must be supplied
+        together, and meet the requirements for :ref:`sec_encoding_ragged_columns`.
         The ``metadata`` and ``metadata_offset`` parameters must be supplied
         together, and meet the requirements for :ref:`sec_encoding_ragged_columns`.
         See :ref:`sec_tables_api_binary_columns` for more information and
@@ -568,6 +578,12 @@ def set_columns(
         :type location: numpy.ndarray, dtype=np.float64
         :param location_offset: The offsets into the ``location`` array.
         :type location_offset: numpy.ndarray, dtype=np.uint32.
+        :param parents: The flattened parents array. Must be specified along
+            with ``parents_offset``. If not specified or None, an empty parents array
+            is stored for each individual.
+        :type parents: numpy.ndarray, dtype=np.int32
+        :param parents_offset: The offsets into the ``parents`` array.
+        :type parents_offset: numpy.ndarray, dtype=np.uint32.
         :param metadata: The flattened metadata array. Must be specified along
             with ``metadata_offset``. If not specified or None, an empty metadata
             value is stored for each individual.
@@ -606,6 +622,8 @@ def append_columns(
 
         The ``flags`` array is mandatory and defines the number of
         extra individuals to add to the table.
+        The ``parents`` and ``parents_offset`` parameters must be supplied
+        together, and meet the requirements for :ref:`sec_encoding_ragged_columns`.
         The ``location`` and ``location_offset`` parameters must be supplied
         together, and meet the requirements for :ref:`sec_encoding_ragged_columns`.
         The ``metadata`` and ``metadata_offset`` parameters must be supplied
@@ -624,6 +642,11 @@ def append_columns(
         :param metadata: The flattened metadata array. Must be specified along
             with ``metadata_offset``. If not specified or None, an empty metadata
             value is stored for each individual.
+        :param parents: The flattened parents array. Must be specified along
+            with ``parents_offset``. If not specified or None, an empty parents array
+            is stored for each individual.
+        :type parents: numpy.ndarray, dtype=np.int32
+        :param parents_offset: The offsets into the ``parents`` array.
         :type metadata: numpy.ndarray, dtype=np.int8
         :param metadata_offset: The offsets into the ``metadata`` array.
         :type metadata_offset: numpy.ndarray, dtype=np.uint32.
@@ -663,7 +686,7 @@ def packset_parents(self, parents):
         must be equal to the number of rows in the table.
 
         :param list parents: A list of list of parent ids, interpreted as numpy int32
-            arrays
+            arrays.
         """
         packed, offset = util.pack_arrays(parents, np.int32)
         d = self.asdict()

python/tskit/trees.py

@@ -147,10 +147,13 @@ class Individual(SimpleContainerWithMetadata):
     :ivar location: The spatial location of this individual as a numpy array. The
         location is an empty array if no spatial location is defined.
     :vartype location: numpy.ndarray
+    :ivar parents: The parent individual ids of this individual as a numpy array. The
+        parents is an empty array if no parents are defined.
+    :vartype parents: numpy.ndarray
     :ivar nodes: The IDs of the nodes that are associated with this individual as
         a numpy array (dtype=np.int32). If no nodes are associated with the
         individual this array will be empty.
-    :vartype location: numpy.ndarray
+    :vartype nodes: numpy.ndarray
     :ivar metadata: The decoded :ref:`metadata <sec_metadata_definition>`
          for this individual.
     :vartype metadata: object