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Just because you don't want to doesn't mean you can't...!
The maths of applying compressive forces to something like a spoke is mostly covered by Euler buckling theory, if you're interested (and didn't know already (and were just being sarcastic)).
hamrack-
It's great that you know about Euler and his buckling theory, but you just don't get to use it here. The point is that you won't apply compressive forces to spokes in 99% of bicycle wheels (I think there was a Mavic wheel model that used compression, once).
So spokes are under a lot of tension, and the magnitude of tension on each spoke will vary during use (particularly when sprinting & disc braking). However! You will never take a spoke down to 0N tension and start compressing it, as there's so much tension on it to begin with. Nor will you apply a bending moment to a spoke. The spoke ends are not constrained enough to start applying those forces. It is only ever simple tension, and in the direction of the spoke.
Ndeipi
When you apply any load other than tension to a wire spoke, get back to us with your maths :-)