简介:Inqualitativeandcombinatorialmatrixtheory,westudypropertiesofamatrixbasedonqualitativeinformation,suchasthesignsofentriesinthematrix.Amatrixwhoseen-triesarefromtheset{+,-,0}iscalledasignpatternmatrix(orsignpattern).Forare-almatrixB,bysgn(B)wemeanthesignpatternmatrixinwhicheachpositive(respec-tively,negative,zero)entryofBisreplacedby+(respectively,-,0).IfAisann×n