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Plotting The Response Of A Digital Filter
Syntax fdplot(dtyminymaxcutoffnumden)
See Also fdplot

Description
Plots the response of a digital filter in the current viewport, where dt is an integer, real, or double-precision scalar specifying the time between sample points; ymin is an integer, real, or double-precision scalar specifying the minimum value on the y-axis; ymax is an integer, real, or double-precision scalar specifying the maximum value on the y-axis; cutoff is an integer, real, or double-precision row vector denoting the cutoff frequencies; num is an integer, real, or double-precision column vector specifying the numerator polynomial for the filter; and den is an integer, real, or double-precision column vector specifying the denominator polynomial for the filter. The y-axis is log-scaled, and the scaling of the x-axis is based on its current settings. Both ymin and ymax must be powers of 10 (e.g., 1, 10, 100).

The response function plotted is

     |             __           |2
     | num[ exp( \/-1 dt w ) ]  |
     ----------------------------
     |             __           |2
     | den[ exp( \/-1 dt w ) ]  |

where w is between pi / (100 dt) and pi / dt.

Example
The example below does not plot any cutoff frequencies because the row vector cutoff has zero column dimension.

clear
#
dt     = 1.
ymin   = 1e-4
ymax   = 1e2
cutoff = fill(0, 1, 0)
num    = {1, 2, 1}
den    = 1
fdplot(dt, ymin, ymax, cutoff, num, den)