# CLOGMAG

## Purpose:

Evaluates the log magnitude squared frequency response of cascade form
filter coefficients.

## Syntax:

CLOGMAG(c, N, r)

(m, p) = CLOGMAG(c, N, r)

c |
- |
A series. The filter coefficients in cascade
format. |

N |
- |
Optional. An integer, the number of output
samples. Defaults to 2048. |

r |
- |
Optional. A real, the sample rate of the data.
Defaults to rate of filter. |

## Returns:

A real series. The log magnitude squared frequency response of the filter.

(m, p) = CLOGMAG(c, N, r) returns
both the log magnitude squared and phase response.

## Example:

W1: elliptic(1,1000.0,200.0,3.0,40.0,250.0)

W2: clogmag(W1, 1024)

W1 contains the bi-quad cascade coefficients of an elliptical
low pass filter. W2 contains 1024 uniformly spaced samples of the log
magnitude squared frequency response of the filter in W1.

## Remarks:

CLOGMAG employs ZFREQ to evaluate **N**
uniformly spaced samples of the complex frequency response of the filter.
The cascade coefficients are converted to direct form and the complex
frequency response is evaluated using the FFT.
The log magnitude squared of the complex frequency response is returned.

CLOGMAG is appropriate
for computing the magnitude response of the IIR filters created by BESSEL, BUTTERWORTH,
CHEBY1, CHEBY2
and ELLIPTIC filter design functions
provided by DADiSP/Filters.

See CPHASE to compute the phase response of
cascade form coefficients.

See CASCADE for more information
on cascade form coefficients.

## See Also:

CASCADE

CPHASE

DADiSP/Filters

FFT

MAGNITUDE

ZFREQ