Merge and Split

This submodule is a post processing step to address tracked cells which merge/split. The first iteration of this module is to combine the cells which are merging but have received a new cell id (and are considered a new cell) once merged. This module uses a minimum euclidian spanning tree to combine merging cells, thus the postfix for the function is MEST. This submodule will label merged/split cells with a TRACK number in addition to its CELL number.

Features, cells, and tracks are combined using parent/child nomenclature. (quick note on terms; “feature” is a detected object at a single time step (see Feature Detection Basics). “cell” is a series of features linked together over multiple timesteps (see Linking). “track” may be an individual cell or series of cells which have merged and/or split.)

Overview of the output dataframe from merge_split

d : xarray.core.dataset.Dataset

xarray dataset of tobac merge/split cells with parent and child designations.

Parent/child variables include:

• cell_parent_track_id: The associated track id for each cell. All cells that have merged or split will have the same parent track id. If a cell never merges/splits, only one cell will have a particular track id.

• feature_parent_cell_id: The associated parent cell id for each feature. All feature in a given cell will have the same cell id.

• feature_parent_track_id: The associated parent track id for each feature. This is not the same as the cell id number.

• track_child_cell_count: The total number of features belonging to all child cells of a given track id.

• cell_child_feature_count: The total number of features for each cell.

Example usage:

d = merge_split_MEST(Track)

merge_split outputs an xarray dataset with several variables. The variables, (with column names listed in the Variable Name column), are described below with units. Coordinates and dataset dimensions are Feature, Cell, and Track.

Variables that are common to all feature detection files:

tobac Merge_Split Track Output Variables

Variable Name	Description	Units	Type
feature	Unique number of the feature; starts from 1 and increments by 1 to the number of features identified in all frames	n/a	int64
cell	Tracked cell number; generally starts from 1. Untracked cell value is -1.	n/a	int64
track	Unique number of the track; starts from 0 and increments by 1 to the number of tracks identified. Untracked cells and features have a track id of -1.	n/a	int64
cell_parent_track_id	The associated track id for each cell. All cells that have merged or split will have the same parent track id. If a cell never merges/splits, only one cell will have a particular track id.	n/a	int64
feature_parent_cell_id	The associated parent cell id for each feature. All feature in a given cell will have the same cell id.	n/a	int64
feature_parent_track_id	The associated parent track id for each feature. This is not the same as the cell id number.	n/a	int64
track_child_cell_count	The number of features belonging to all child cells of a given track id.	n/a	int64
cell_child_feature_count	The number of features for each cell.	n/a	int64