or why “… matrix inversion is singular”?

To test your predictors, use:

Sources\collinearity-diagnostics-matlab

ne_check_sdm_for_collinearity.m

Based on: http://www.subcortex.net/research/code/collinearity-diagnostics-matlab-code by Brian Lau

Developed by Jurriaan Born

http://support.brainvoyager.com/available-tools/53-user-developed-tools/238-brainvoyager-analysis-predictor-tool.html