How to define custom numerical similarity scores in Lucene ?

[Patrick Diviacco <pa...@gmail.com>]

Queries and Documents in my collection have multiple fields: some numeric
and some textual.

I know how to define custom Similarity classes per field in Lucene: so I
have my textualSimilarity (tf.idf based) and a numericalSimilarity class
(both extending Similarity)

I'm now studying how to implement such numericalSimilarity. I have a math
formula " (queryNumber - docNumber) / normalization factor) to define the
similarity between numeric fields.

But how can I implement this formula in the numericalSimilarity class ?
Which methods should I extend ?

thanks