sacpz2resp.py - Convert a Sac Pole Zero file into a Amplitude/Phase Response
pz2resp.py - Convert a Sac Pole Zero file into a Resp formatted file 

sacpz2resp.py --help 

Option -f filename
   Sac Pole Zero file should be in an output format as output from rdseed
   Keys: 
      ZEROS nzeros
      zero [ real, imaginary ]
      ...
      POLES npoles
      pole [ real, imaginary ]
      ...
      CONSTANT constant value

Option -u units
   dis - Displacement   [ Zeros are not changed ]
   vel - Velocity       [ One Zero is removed ]
   acc - Acceleration   [ Two Zeros are removed ]
   
Output on stdout
   Frequency (Hz) Amplitude (meters) Phase (radians)

Internals:
  freq = frequency      Hz 
  z_i                   Zeros
  p_i                   Poles
  min_freq, max_freq    Minimum and Maximum Frequencies 
  npts                  Number of Points to Evaluate 
  delta                 Spacing in seconds of the time series 

                 (max_freq - min_freq)
  delta_freq = ------------------------
                    (npts * delta)

  w = 2 * pi * f         Angular Frequency, Radians

              (w-z_0) (w-z_1) ... (w-z_n)
  R(w) = C * -----------------------------
              (w-p_0) (w-p_1) ... (w-p_n)