function?MIhat?=?nmi（?A?B?）
?%NMI?Normalized?mutual?information
?%?http://en.wikipedia.org/wiki/Mutual_information
?%?http://nlp.stanford.edu/IR-book/html/htmledition/evaluation-of-clustering-1.html
?%?Author:?http://www.cnblogs.com/ziqiao/???[2011/12/15]?

if?length（?A?）?~=?length（?B）
?????error（‘length（?A?）?must?==?length（?B）‘）;
end
?total?=?length（A）;
?A_ids?=?unique（A）;
?A_class?=?length（A_ids）;
?B_ids?=?unique（B）;
?B_class?=?length（B_ids）;
?%?Mutual?information
?idAOccur?=?double?（repmat（?A?A_class?1）?==repmat（?A_ids‘?1?total?））;
idBOccur?=?double?（repmat（?B?B_class?1）?==?repmat（?B_ids‘?1?total?））;
idA