Yes. Look at PearsonCorrelationSimilarity. It implements ItemSimilarity so it can compute a Pearson correlation between ratings for two items. Pearson is the covariance divided by the product of the standard deviations. So, just multiply the similarity value you get by the standard deviations of the items' preference values.
The variance of each item's preference values is simply the square of the standard deviation, if that's what you mean. You can use RunningAverageAndStdDev to help compute standard deviation if you like. On Thu, Nov 26, 2009 at 3:14 PM, jamborta <[email protected]> wrote: > > hi guys, > just wondering if you have a method implemeted which would calculate the > covariance between two items. and the variance of an item. I looked > itemSimilarities but that one does something different. > > thanks > Tama > -- > View this message in context: > http://old.nabble.com/Mahout-Taste-covariance-between-two-items-tp26530825p26530825.html > Sent from the Mahout User List mailing list archive at Nabble.com. > >
