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# polyscale() - Signal Processing

### Syntax

### Example

### Output / Return Value

### Limitations

### Alternatives / See Also

### Reference

b = polyscale(a,alpha) scales the roots of a polynomial in the z-plane, where a is a vector containing the polynomial coefficients and alpha is the scaling factor.If alpha is a real value in the range [0 1], then the roots of a are radially scaled toward the origin in the z-plane. Complex values for alpha allow arbitrary changes to the root locations.

b = polyscale(a,alpha)

Roots of UnityOpen This Example Express the solutions to the equation as the roots of a polynomial. Plot the roots in the complex plane. pp = [1 0 0 0 0 0 0 -1]; zplane(pp,1) Scale the roots of p in and out of the unit circle. Plot the results.hold on for sc = [1:-0.2:0.2 1.2 1.4]; b = polyscale(pp,sc); plot(roots(b),'o') end axis([-1 1 -1 1]*1.5) hold off Bandwidth Expansion of LPC Speech SpectrumOpen This ExampleLoad a speech signal sampled at . The file contains a recording of a female voice saying the word "MATLAB®."load mtlb Model a 100-sample section of the signal using a 12th-order autoregressive polynomial.Ao = lpc(mtlb(1000:1100),12); Ax = polyscale(Ao,0.85); Perform bandwidth expansion of the signal by scaling the roots of the autoregressive polynomial by 0.85. Plot the zeros, poles, and frequency responses of the models.subplot(2,2,1) zplane(1,Ao) title('Original') subplot(2,2,3) zplane(1,Ax) title('Flattened') subplot(1,2,2) [ho,w]=freqz(1,Ao); [hx,w]=freqz(1,Ax); plot(w/pi,abs([ho hx])) legend('Original','Flattened')