build a polynomial matrix from its coefficients
P = inv_coeff(C) P = inv_coeff(C, d) P = inv_coeff(C, d, varname)
a big matrix of the coefficients
a polynomial matrix degree. The optional parameter with default value d=-1+size(C,'c')/size(C,'r')
a string giving the polynomial variable name (default value 'x').
P=inv_coeff(Mp,k), when k is compatible with Mp
size, returns a polynomial matrix of degree k. C=[C0,C1,...,Ck] and
P= C0 + C1*x +... +Ck*x^k.