Filters a given data set with a filter whose coefficients are specified.  This can be used for both IIR and FIR filters.  The general form of the time domain difference equation of the filter is given as:

a1*y(t) = b1*x(t) + b2*x(t-1) + … bm*x(t-m) – a2*y(t-1) - … an*y(t-n)

Syntax

OutputData = Filter(Num, Den, InputData)

Arguments

Name

Description

Num

Vector of numerator coefficients in descending power of z. These are associated with the input.

Den

Vector of denominator coefficients in descending power of z. These are associated with the output.  The first element must be non-zero.

InputData

A vector of data (real) to be filtered.

Output

Name

Description

OutputData

A vector of filtered data.  Same size as the input data.

Example

Filter a set of data (stored in variable data) with a filter whose numerator and denominator coefficients are given by vectors b and a, with zero initial conditions.

Syntax

Filtered = Filter(b,a,data)

Result

Filtered is a vector containing the filtered data.

Comments

Normally the coefficients would be obtained from a suitable filter design technique.

See Also:

Butter

Cheby1

Cheby2

Ellip

FiltFilt