Compute frequency response of a digital filter.
Given the numerator (b) and denominator (a) of a digital filter compute its frequency response.
jw jw jmwjw B(e) b[0] + b[1]e + .... + b[m]e
 H(e) = — = ————————————
jw jw jnwA(e) a[0] + a[2]e + .... + a[n]e
Parameters:  b : ndarray
a : ndarray
worN : {None, int}, optional
whole : {0,1}, optional


Returns:  w : ndarray
h : ndarray
