Infinite Impulse Response Filter (IIR Filter)

This operator implements an infinite impulse response filter.

It returns a weighted average of the current ping and the calculated previous ping.

Echoview accepts a single variable of the following types as input:

See: IIR algorithm.

Settings

The Infinite Impulse Response Filter Variable Properties dialog box pages include (common) Variable Properties pages and these operator pages:

Operands page

IIR Filter page

Setting

Description

Coefficient

Enter the coefficient to be used to alter signal content.

Algorithm

IIR filter

The result for any given data point may be written as:

Result(0,d) = Operand(0,d)
Result
(p,d) = C * Operand(p,d) + (1-C) * Result(p-1,d)            where p>0

Where:

p identifies the ping
d
identifies the data point (each ping contains a number of data points)
C
is the coefficient entered on the IIR page of the Variable Properties dialog box.
Result
(p,d) is the value of the data point d in ping p in the resulting variable.
Operand
(p,d) is the value of the data point d in ping p in the operand variable.

Hence, if C = 1 the filter will make a copy of the operand variable, and if C = 0, the filter will make a copy of the operand variable with each ping containing the values of ping 0 from the operand variable.

Notes:

See also

About virtual variables
Operator licensing in Echoview