[Fix] getData: wrong mat files were picked

Signed-off-by: oleg komarov <o.komarov11@imperial.ac.uk>
[Minor] getData: varnames pre-processing

Signed-off-by: oleg komarov <o.komarov11@imperial.ac.uk>
[Change] makeMasterFile: changed the id mapping, more robust and straightforward.

Signed-off-by: oleg komarov <o.komarov11@imperial.ac.uk>