Extract several matrices from single column vector

Question

Cedric Kotitschke 2023-10-24

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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2037801-extract-several-matrices-from-single-column-vector

回答： Cedric Kotitschke 2023-10-24

采纳的回答： Cedric Kotitschke

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Hey,

I have three matrices

A, B, C, D which I flatten to a single column vector:

J = [A(:); B(:); C(:); D(:)]

How can I used indexing to extract the matrices again? Unfortunately, I cannot use reshape because J is a vector of realp objects.

Basically I want to do this:

A = J(idxA);
B = J(idxB);
C = J(idxC);
D = J(idxD);

Thanks for your help!

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Cedric Kotitschke 2023-10-24

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n = 20;
% Create genmat object
pGenmat = [];
for i = 1:n
    pGenmat = [pGenmat; realp(sprintf('p%d', i), i)];
end
% Create double array with same size
pDouble = reshape(1:n, n, 1);
% Reshape double array (no error)
pDouble_reshaped = reshape(pDouble, 4, 5);
% Reshape genmat (error)
pGenmat_reshaped = reshape(pGenmat, 4, 5);

Bruno Luong 2023-10-24

I don't know genmat objects. I'll delete my answer.

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Answer 1

Cedric Kotitschke 2023-10-24

0
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此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/2037801-extract-several-matrices-from-single-column-vector#answer_1339561

在 MATLAB Online 中打开

For everyone who also struggles with this, here's my solution. It is clunky but that's only because genmat objects are buggy when it comes to reshaping and matrix indexing.

The input to this example are the parameterset, which holds names, values and nominal values of some parameters and the function handle which includes trimming and linearizing of a simulink model, given the parameterset.

% Utility function
function [J, sys] = getSys(x, parameterset, fun)
    parameterset.Values = x;
    sys = fun(parameterset);
    J = [sys.A(:); sys.B(:); sys.C(:); sys.D(:)];
end
% Get nominal system
[J0, sys0] = getSys(parameterset.NominalValues, parameterset, fun);
% Compute jacobian
f = @(x) getSys(x, parameterset, fun);
x0 = parameterset.NominalValues;
jac = roughjacobianest(f, x0); 
% Create tunable parameters
p = [];
for param = parameterset.Elements
    p = [p; realp(param.Name, param.NominalValue)];
end
% Create linear system
J = J0 + jac * (p - parameterset.NominalValues(:));
% This workaround is necessary because both reshaping and proper
% indexing is buggy when it comes to genmat objects
na = numel(sys0.A);
szA = size(sys0.A);
Ja = J(1:na);
nb = numel(sys0.B);
szB = size(sys0.B);
Jb = J((na+1):(na+nb));
nc = numel(sys0.C);
szC = size(sys0.C);
Jc = J((na+nb+1):(na+nb+nc));
nd = numel(sys0.D);
szD = size(sys0.D);
Jd = J((na+nb+nc+1):(na+nb+nc+nd));
A = genmat(zeros(szA));
for i = 1:na
    [idxRow, idxCol] = ind2sub(szA, i);
    A(idxRow, idxCol) = Ja(i);
end
B = genmat(zeros(szB));
for i = 1:nb
    [idxRow, idxCol] = ind2sub(szB, i);
    B(idxRow, idxCol) = Jb(i);
end
C = genmat(zeros(szC));
for i = 1:nc
    [idxRow, idxCol] = ind2sub(szC, i);
    C(idxRow, idxCol) = Jc(i);
end
D = genmat(zeros(szD));
for i = 1:nd
    [idxRow, idxCol] = ind2sub(szD, i);
    D(idxRow, idxCol) = Jd(i);
end
sys = ss(A, B, C, D);