Method Lk

pattern/vector/__init__.py:1230–1239

Prunes candidate sets whose frequency < support threshold. Returns a dictionary of (candidate set, frequency)-items.

(self, sets, candidates, support=0.0)

        return Ck
        
    def Lk(self, sets, candidates, support=0.0):
        """ Prunes candidate sets whose frequency < support threshold.
            Returns a dictionary of (candidate set, frequency)-items.
        """
        Lk, x = {}, 1.0 / (len(sets) or 1) # relative count
        for s1 in candidates:
            for s2 in sets:
                if s1.issubset(s2):
                    Lk[s1] = s1 in Lk and Lk[s1]+x or x
        return dict((s, f) for s, f in Lk.items() if f >= support)

    def __call__(self, sets, support=0.5):
        """ Returns a dictionary of (set(features), frequency)-items.