Calculates the derivative of the spatial average effect
eta_D_der(
parm,
matList,
adj_positions,
interaction_effects = list(),
index = 4
)the derivative of the spatial average effect
the parameter
a list of the matrices (pairwise+spatial)
the positions of the spatial effect (if embedded)
the interaction effect pairs (2-pair-name-vectors)
position of the spatial effect within the list