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# filtic() - Signal Processing

### Syntax

### Example

### Output / Return Value

### Limitations

### Alternatives / See Also

### Reference

z = filtic(b,a,y,x) finds the initial conditions, z, for the delays in the transposed direct-form II filter implementation given past outputs y and inputs x. The vectors b and a represent the numerator and denominator coefficients, respectively, of the filter's transfer function.The vectors x and y contain the most recent input or output first, and oldest input or output last.x=[x(−1),x(−2),x(−3),…,x(−n)]y=[y(−1),y(−2),y(−3),…,y(−m)]where n is length(b)-1 (the numerator order) and m is length(a)-1 (the denominator order). If length(x) is less than n, filtic pads it with zeros to length n; if length(y) is less than m, filtic pads it with zeros to length m. Elements of x beyond x(n-1) and elements of y beyond y(m-1) are unnecessary so filtic ignores them.Output z is a column vector of length equal to the larger of n and m. z describes the state of the delays given past inputs x and past outputs y.z = filtic(b,a,y) assumes that the input x is 0 in the past.The transposed direct-form II structure is shown in the following illustration. n – 1 is the filter order. filtic works for both real and complex inputs.

z = filtic(b,a,y,x)z = filtic(b,a,y)

Requires vector inputs.