Signal Processing Toolbox

eqtflength

Make the lengths of a transfer function's numerator and denominator equal.

Syntax

[b,a] = eqtflength(num,den)

Description

[b,a] = eqtflength(num,den) modifies the vector num and/or the vector den, so that the resulting output vectors b and a have the same length. The input vectors num and den may have different lengths. The vector num represents the numerator polynomial of a given discrete-time transfer function, and the vector den represents its numerator. The resulting numerator b and denominator a represent the same discrete-time transfer function, but these vectors have the same length.

Use eqtflength to obtain a numerator and denominator of equal length before applying transfer function conversion functions such as tf2ss and tf2zp to discrete-time models.

Examples

num = [1 0.5];
den = [1 0.75 0.6 0];
[b,a] = eqtflength(num,den)
b =
    1.0000    0.5000         0
a =
    1.0000    0.7500    0.6000

Algorithm

eqtflength(num,den) appends zeros to either num or den as necessary. If both num and den have trailing zeros in common, these are removed.

See Also

tf2ss	Convert a transfer function to state-space form.
tf2zp	Convert a transfer function to zero-pole-gain form.

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