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Total number of decision variables in system of LMIs


ndec = decnbr(lmisys)


The function decnbr returns the number ndec of decision variables (free scalar variables) in the LMI problem described in lmisys. In other words, ndec is the length of the vector of decision variables.


For an LMI system lmis with two matrix variables X and Y such that

  • X is symmetric block diagonal with one 2-by-2 full block, and one 2-by-2 scalar block

  • Y is 2-by-3 rectangular,

the number of decision variables is

ndec = decnbr(LMIs)

ndec = 

This is exactly the number of free entries in X and Y when taking structure into account (see decinfo for more details).

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Introduced before R2006a