# How to quantitatively measure strength of friendship using observable factors?

Is there any quantitative measure associated with the strength of a friendship or relationship? Ideally it should be able to be calculated based on observable factors, but should not require interaction with the subjects, just observation.

Note: Specifically I am analyzing fictionalized novels.

• In what arena? There are several algorithms for calculating strength of relationship in a Facebook-type context, and I think there are also coding systems for verbal/nonverbal behavior between the pair, but they generally restrict themselves in scope. – Krysta Nov 4 '14 at 13:43
• +1 for systemizing human behaviour – user6939 Nov 4 '14 at 19:38

• When I've seen the question title I actually hoped someone might come with $\frac{N}{neurons}$ equation :) (N stands for newtons) – Tomáš Zato - Reinstate Monica Nov 24 '14 at 22:42