max_abs_eigval: if < 1, then the VAR will be stable
sparsity_pattern: The sparsity pattern that should be simulated. Options are: "none" for a dense VAR, "lasso" for a VAR with random zeroes, and "hvar" for an elementwise hierarchical sparsity pattern
sparsity_options: Named list of additional options for when sparsity pattern is lasso or hvar. For lasso the option num_zero
determines the number of zeros. For hvar, the options zero_min (zero_max) give the minimum (maximum) of zeroes for each variable in each equation, and the option zeroes_in_self (boolean) determines if any of the coefficients of a variable on itself should be zero.
decay: How fast should coefficients shrink when the lag increases.
...: Not currently used
Returns
Returns a coefficient matrix in companion form of dimension kpxkp.