Impulse response invariant discretization of distributed order low-pass filter

Compute a discrete-time transfer function to approximate a distributed order low pass filter.

irid_dolpf function is prepared to compute a discrete-time finite dimensional (z) transfer function to approximate a distributed order integrator ((c^r)/(b-a))*int(1/(s+c)^r,r,a,b), where "s" is the Laplace transform variable. Where 'a' and 'b' are arbitrary real numbers in the range of (0.5,1), and a<b. c>=0, 'p' and 'q' are integer and p>=q.