Inverse the (m,m,T) array of matrices for m<=4
mult_inv_small(A)
dd vector of determinants (Tx1)
multi-dimensional array
equivalent to the following for loop:
for (i in 1:T){ y[ , ,i] = inv(A[,,i]) }
This function is based on the "mult_inv_small" function by Le and Singleton (2018).
"A Small Package of Matlab Routines for the Estimation of Some Term Structure Models."
(Euro Area Business Cycle Network Training School - Term Structure Modelling).
Available at: https://cepr.org/40029