The formula here is just a weighted average. You have to divide by the sum of the weights to normalize the result.
If similarity(i,n) is small, then the denominator is small, yes. But so is the numerator. This does not make the result large. 2011/11/3 myn <[email protected]>: > in the pagehttps://issues.apache.org/jira/browse/MAHOUT-420 > > Prediction(u,i) = sum(all n from N: similarity(i,n) * rating(u,n)) / sum(all > n from N: abs(similarity(i,n))) > > why must devide sum(all n from N: abs(similarity(i,n))), if similarity(i,n) > is quite small , i don`t want redommend that item,i only want recommend very > similary item. it seems that not work very well. > > > >
