When saving large arrays with repeated elements, data compression can save a huge amount of space.

This BSD licensed toolbox by Kota Yamaguchi uses matlab java interface to support gzip and zlib based compression. Use it for now.

https://www.mathworks.com/matlabcentral/fileexchange/39526-byte-encoding-utilities

For octave, need to find alternatively solution.

Ultimately, need a mex-based gzipencode/zlibencode package for portability.