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From Jonathan Seale <>
Subject Row Similarity
Date Thu, 14 May 2015 03:15:19 GMT

I have an astrophysical application for Mahout that I need help with.

I have 1-dimensional stellar spectra for many, many stars. Each spectrum
consists of a series of intensity values, one per wavelength of light. I
need to be able to find the cosine similarity between ALL pairs of stars.
Seems to me this is simply a user-user similarity problem where I have
stars instead of users, wavelengths instead of items, and intensities
instead of ratings/clicks.

But I'm having difficulty using mahout's row similarity package (I'm new to
this, and these days astronomers code pretty exclusively in python). I know
that I must have to 1) create a sparse matrix where each row is a star,
columns are wavelengths, and the values are intensity, and 2) implement row
similarity. But I'm just not sure how to do it. Anyone have a good resource
or be willing to help? I could probably offer some compensation to anyone
that would be willing to provide a little focussed, personalized assistance.


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