Bayes Classifier
Background knowledge:
By comparing values of P(c(Xˉ)=1∣x1​,...,xd​) and P(c(Xˉ)=−1∣x1​,...,xd​), one can determine whether or not the active user likes Xˉ. To predict P(c(Xˉ)=1), the following expression is used.
P(c(Xˉ)=1)=∣DL​∣+2⋅α∣DL+​∣+α​ In this expression, $$
f(x)=x∗e2piiξx