How to extract idpoly property to workspace

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demos serghiou
demos serghiou 2022-12-31
回答： Star Strider 2022-12-31
Hi, how can I extract and put in my workspace variable A and NoiseVariance from idpoly to do further processing?

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Star Strider
Star Strider 2022-12-31
Ran in:
There are several properties that can be retrieved from the System Identification Toolbox ‘data’ objects. See the documentation on idpoly and others for details.
Try something like this —
LD = load(websave('idpoly','https://www.mathworks.com/matlabcentral/answers/uploaded_files/1248207/idpoly.mat'))
LD = struct with fields:
a: [1×0 idpoly]
a = LD.a
a = Discrete-time AR model: A(z)y(t) = e(t) A(z) = 1 + (-7.954 - 0.3i) z^-1 + (26.36 + 2.3i) z^-2 + (-45.35 - 7.6i) z^-3 + (38.88 + 13i) z^-4 + (-7.968 - 12i) z^-5 + (-8.478 + 6.2i) z^-6 + (-3.663 - 2.7i) z^-7 + (11.26 + 2.5i) z^-8 + (0.9163 + 0.051i) z^-9 + (-7.189 - 2.7i) z^-10 + (-4.175 + 0.46i) z^-11 + (12.39 + 3.7i) z^-12 + (-4.697 - 5.7i) z^-13 + (-6.017 + 3.4i) z^-14 + (6.773 + 3.6i) z^-15 + (-1.439 - 10i) z^-16 + (-1.529 + 11i) z^-17 + (1.173 - 5.9i) z^-18 + (-0.3192 + 1.7i) z^-19 + (0.0307 - 0.21i) z^-20 Sample time: 1 seconds Parameterization: Polynomial orders: na=20 Number of free coefficients: 20 Use "polydata", "getpvec", "getcov" for parameters and their uncertainties. Status: Estimated using AR ('burg/now') on time domain data (complex) "est_x1". Fit to estimation data: 100% FPE: 2.355e-25, MSE: 2.008e-25
Coefficients = a.A
Coefficients =
1.0000 + 0.0000i -7.9541 - 0.2965i 26.3582 + 2.3178i -45.3509 - 7.5709i 38.8797 +13.0764i -7.9676 -12.3483i -8.4781 + 6.1760i -3.6634 - 2.7037i 11.2582 + 2.5171i 0.9163 + 0.0513i -7.1889 - 2.6674i -4.1745 + 0.4615i 12.3895 + 3.7428i -4.6974 - 5.6726i -6.0167 + 3.4192i 6.7730 + 3.5819i -1.4387 -10.4534i -1.5295 +10.7850i 1.1733 - 5.9423i -0.3192 + 1.7405i 0.0307 - 0.2143i
Variable = a.Variable
Variable = 'z^-1'
Structure = a.Structure
Structure = A: [1×1 param.Continuous] IODelay: [1×0 double] IntegrateNoise: 0 AR model structure.
You can use the ‘Coefficients’ vector with polyval to evaluate it.
t = linspace(0, 1.5, 150);
A = polyval(Coefficients, t);
figure
plot(t, real(A), 'DisplayName','Re(A)')
hold on
plot(t, imag(A), 'DisplayName','Im(A)')
plot(t, abs(A), 'DisplayName','|A|')
hold off
grid
legend('Location','best')
.

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