This function actually does the heavy lifting once we have a matrix of predicted probabilities from a model, plus the vector of observed outcomes. The reason to have it here in a single function is that we don't replicate it in each function that accomodates a JAGS, BUGS, RStan, etc. object.
new_mcmcRocPrc(pred_prob, yvec, curves, fullsims)
a \[N, iter\]
matrix of predicted probabilities
a numeric(N)
vector of observed outcomes
include curve data in output?
collapse posterior samples into single summary?