Programmer Guide/Command Reference/EVAL/iir1: Difference between revisions
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{{DISPLAYTITLE: | {{DISPLAYTITLE:{{SUBPAGENAME}}}} | ||
Create and/or apply an IIR filter. | |||
---- | ---- | ||
;Usage 1: <code>iir1(<var>f1</var>, <var>f2</var> {, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>})</code> | ;Usage 1: <code>iir1(<var>f1</var>, <var>f2</var> {, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>})</code> | ||
| Line 23: | Line 23: | ||
:;<var>c</var>: IIR filter coefficients (see '''Usage 1''') | :;<var>c</var>: IIR filter coefficients (see '''Usage 1''') | ||
:;<var>z</var>: the filter state (delay); must be a matrix with the same dimensions as ''c'' | :;<var>z</var>: the filter state (delay); must be a matrix with the same dimensions as ''c'' | ||
: | ::notes: | ||
::*The matrix should be initialized with zeros (e.g.: <code>#z := eval init($#c[!nrow],$#c[!ncol],0)</code>) | |||
::*The values of ''z'' are changed (''z'' must be a ''reference'' to a [[Programmer_Guide/Shell_Items/Table|table item]] | |||
:;<var>x</var>: the signal sample (scalar) or the signal vector to be filtered | :;<var>x</var>: the signal sample (scalar) or the signal vector to be filtered | ||
:; | :; | ||
;See also: | ;See also: [[Programmer_Guide/Command_Reference/EVAL/fir1|fir1]] | ||
[[Programmer_Guide/Command_Reference/EVAL#Functions|<function list>]] | |||
Revision as of 12:55, 11 April 2011
Create and/or apply an IIR filter.
- Usage 1
iir1(f1, f2 {, m, rp, rs, inv, type})- f1, f2
- the lower and upper cutoff frequency; both values must be specified as relative frequencies (f / sampling-rate); 0 <= f1 < f2 <= 0.5
- m
- the filter order (default=5)
- rp
- the desired passband ripple in dB; 0 < rp (default=0.5)
- rs
- the desired stopband damping level in dB; 0 < rs (default=40)
- inv
- invert filter response (0=no, 1=yes); if this value is set to 1, the filter frequency response is inverted and f1/f2 are the boundaries of the stopband
type: the type of the filter
- {class=keinrahmen"
|type=1 ||... Butterworth filter |type=2 ||... Chebyshev filter |type=3 ||... elliptic filter (this is the default)
- Result
- The function computes the filter coefficients for the IIR defined by the arguments and returns a matrix c with 2 columns. The first column (c[*,0]) contains the denominator coefficients (poles) and the second (c[*,1]) the nominator coefficients (zeros). The matrix c can be used to apply the filter to a signal (see Usage 3).
- Usage 2
iir1(f1, f2, m, rp, rs, inv, type, x)- f1, f2, m, rp, rs, inv, type
- see Usage 1
- x
- a vector containing the source signal
- Result
- The function computes the filter coefficients for the IIR defined by the arguments and applies it to the signal x. The result has the same type as the input signal x and containes the filtered signal.
- Usage 3:
iir1(c, z, x{, s})- c
- IIR filter coefficients (see Usage 1)
- z
- the filter state (delay); must be a matrix with the same dimensions as c
- notes:
- The matrix should be initialized with zeros (e.g.:
#z := eval init($#c[!nrow],$#c[!ncol],0)) - The values of z are changed (z must be a reference to a table item
- The matrix should be initialized with zeros (e.g.:
- x
- the signal sample (scalar) or the signal vector to be filtered
- See also
- fir1
