Test for *any* density dependence

[davharris]

i.e., is the slope at high densities different from the slope at low densities?

Criteria at high density:

• If slope is negative, overcompensation.
• If slope is zero, perfect compensation
• If slope is positive, partial compensation
• If slope is R_0 (or r or whatever), no density dependence at all
• If slope is greater than R_0 (or whatever), then positive density dependence

[davharris]

Note that the R thingy should be calculated under the assumption of no density dependence, i.e. with a linear regression passing through zero.