The method he uses is kind of funny  is ,   um ,  he starts with  he has a set of M of them. Um , he  and then  he uses that to classify  I mean , he t he tries , um ,  using  just M minus one of them. So there are M possible subsets of this  length - M vector. He tries classifying , using each of the M  possible sub - vectors.
Hmm.
Whichever sub - vector ,  um , works the  the best , I guess , he says   the  the fe feature that didn't use was the most useless feature ,
Y yeah. Gets thrown out. Yeah.