Draw the dyadic residual variance s2 from its inverse-gamma full
conditional. The residual matrix E = Z - offset is decorrelated
within reciprocal dyad pairs and along the diagonal, and the pooled sum of
squares (together with an optional scaled-inverse-chi-square prior) yields
the posterior draw.
rs2_fc(Z, rho, offset = 0, nu0 = NULL, s20 = NULL)a single draw of s2
n x n normal relational matrix
current within-dyad correlation
matrix conformable with Z; Z - offset is treated
as pure dyadic noise (so it should carry the additive and multiplicative
mean structure)
prior degrees of freedom (defaults to 1)
prior scale for s2; when NULL the empirical mean of the
decorrelated squared residuals is used so the prior sits at the data scale
lame authors