For an AME fit, a dyad whose covariate value is missing cannot contribute a
covariate-coefficient observation. Rather than silently imputing the missing
covariate as 0 (which biases the coefficient when the covariate is not
mean-centred), the dyad is treated as an unobserved tie and handled by data
augmentation. This helper sets the affected Y cells to NA;
lame already does this internally, and this brings
ame into line.
.ame_propagate_cov_na(Y, Xrow = NULL, Xcol = NULL, Xdyad = NULL)Y with covariate-missing cells set to NA.
an n x n response matrix.
row, column and dyadic covariates (or NULL).