# API Reference


## Classes


[indices](indices.md#spector.indices)  
A sparse boolean array, i.e., set of indices.

[vector](vector.md#spector.vector)  
A sparse array of index keys mapped to numeric values.

[matrix](matrix.md#spector.matrix)  
A sparse vector of vectors.


## Functions


[groupby()](groupby.md#spector.groupby)  
Generate unique keys with associated groups.