# grpdelay

Compute digital filter group delay values.

## Syntax

[gd,w] = grpdelay(b,a)

[gd,w] = grpdelay(b,a,n)

[gd,w] = grpdelay(b,a,n,'whole')

[gd,f] = grpdelay(b,a,n,fs)

[gd,f] = grpdelay(b,a,n,'whole',fs)

gd = grpdelay(b,a,w)

gd = grpdelay(b,a,f,fs)

grpdelay(...)

## Inputs

b
The numerator polynomial coefficients of the filter.
Type: double
Dimension: vector
a
The denominator polynomial coefficients of the filter.
Type: double
Dimension: vector
n
The number of frequencies at which to compute the delay. For frequencies in Hz, when 'whole' is specified the range is [0,fs), and [0,fs/2) otherwise. For normalized angular frequecies in radians, when 'whole' is specified the range is [0, 2*pi), and [0,pi) otherwise.
Default: 512 (use []).
Type: integer
Dimension: scalar
f
The frequencies (in Hz) at which the delay is computed.
Type: double
Dimension: scalar | vector
w
The normalized angular frequencies (in radians) at which the delay is computed. The normalized Nyquist frequency is pi radians.
Type: double
Dimension: scalar | vector
fs
The sampling frequency (in Hz).
Type: double
Dimension: scalar

## Outputs

gd
The group delay values in units of samples.
Type: double
Dimension: scalar | vector
f
The frequencies (in Hz) at which the delay is computed.
Type: double
Dimension: scalar | vector
w
The normalized angular frequencies (in radians) at which the delay is computed.
Type: double
Dimension: scalar | vector

## Example

Plot the group delay of a fourth order Chebyshev I low pass digital filter with a 200 Hz cutoff frequency and a 1000 Hz sampling frequency.
fc = 200;
fs = 1000;
[b,a] = cheby1(4,1,fc/(fs/2));
grpdelay(b,a,[],fs);