Hi all, I'm using the "lin" function to numerically linearize a 6DoF aircraft model for control system analysis. The function works very well and I thank the authors for their effort. I'm only facing issues when documenting my studies as I could not find any reference to the algorithm/technique used in the linearization code. I have a general idea of the theory, for example as mentioned in these reports: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/19780020922.pdf http://www.nasa.gov/centers/dryden/pdf/88021main_H-1295.pdf But I could not understand specifically the need for a "colcomp" operation. Am I right in assuming that it is done to ensure non-singularity of the state/input perturbation matrix? Also an explanation of the final matrix division performed to obtain the A,B,C,D system matrices. I am supposed to get D as zero, but there are non-zero terms (approx 10^-15) etc which I ignore. Am I correct in ignoring them or do I have to apply some corrections to A/B/C matrices to compensate?