logical value that controls whether informed priors are
supplied to the model for both \(\delta^{15}\)N and
\(\delta^{15}\)C baselines. Default is FALSE meaning the model will
use uninformed priors, however, the supplied data.frame needs values
for both \(\delta^{15}\)N and \(\delta^{15}\)C baseline
(c1, c2, n1, and n2).