You're getting no responses (probably) because you're asking for a reference to a detailed walkthrough that probably doesn't exist, as your subject is very specific and is relatively simple mathwise. A better approach for general topic posting in future is to describe a problem (as you have) and ask for any help, not necessarily a reference.
That said, approaches could be to:
1. add the attributes and use the sum.
2. multiply the attributes and use the product.
3. multiply each attribute by some factor and sum the results of those products.
Perhaps you can provide some additional information if one of those approaches doesn't fit the situation.
Edited by Buckeye, 23 June 2014 - 06:17 AM.