How to define a matrix which changes its size in every iteration of loop?

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zahid fazal 2021-2-20

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评论： Rena Berman 2021-5-6

T = 50;    %total iteration 
x = randn(T,1); %input
pw =[0,0,0,0,0,1,-0.3,0.2];    % primary path TF 
d = filter(pw, 1, x);          % desiresd input
mu = 0.1;  %step size
g = 1e-12; %gamma
%p = 2;     %projection order
N = 8;    %no of taps
Pmax = 4;
w = zeros(N,1); % weights of controller
y = zeros(1,T); % output of controller
%Xi = zeros(p,N); %input matrix  
e_cont = zeros(T,1); %residual noise
p = zeros(T,1);
p(1)=Pmax;
for i=1:T
    Xi(2:p(i),:) = Xi(1:p(i),:);
    Xi(1,:) = [ x(i:-1:max(i-N+1,1)).',zeros(1,max(N-i,0)) ];
    di = transpose([ d(i:-1:max(i-p(i)+1,1)).',zeros(1,max(p(i)-i,0)) ]);
    Yi = Xi*w;
    err= di-Yi;
    sqe = err.^2;
    UT = (mu*p(i)+2)*var/(2-mu);
    LT = (mu*(p(i)-1)+2)*var/(2-mu);
    if sqe(p(i)) > UT
        p(i+1) = min(p(i)+1,Pmax);
    elseif sqe(p(i))<= LT
        p(i+1) = max(p(i)-1,1);
    else
        p(i+1) = p(i);
    end
    w = w + mu*Xi'*inv(g*eye(p(i))+Xi*Xi')*(di-Yi);
    e_cont(i)= err(p(i));
end;

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Stephen23 2021-2-23

编辑：Stephen23 2021-2-23

在 MATLAB Online 中打开

Original question by zahid fazal retrieved from Google Cache:

https://web.archive.org/web/20210223064945/https://webcache.googleusercontent.com/search?q=cache%3AvhRjTWsjouUJ%3Ahttps%3A%2F%2Fwww.mathworks.com%2Fmatlabcentral%2Fanswers%2F751039-how-to-define-a-matrix-which-changes-its-size-in-every-iteration-of-loop

https://web.archive.org/web/20210223070420/https://www.mathworks.com/matlabcentral/answers/751039-how-to-define-a-matrix-which-changes-its-size-in-every-iteration-of-loop

How to define a matrix which changes its size in every iteration of loop?

T = 50;    %total iteration 
x = randn(T,1); %input
pw =[0,0,0,0,0,1,-0.3,0.2];    % primary path TF 
d = filter(pw, 1, x);          % desiresd input
mu = 0.1;  %step size
g = 1e-12; %gamma
%p = 2;     %projection order
N = 8;    %no of taps
Pmax = 4;
w = zeros(N,1); % weights of controller
y = zeros(1,T); % output of controller
%Xi = zeros(p,N); %input matrix  
e_cont = zeros(T,1); %residual noise
p = zeros(T,1);
p(1)=Pmax;
for i=1:T
    Xi(2:p(i),:) = Xi(1:p(i),:);
    Xi(1,:) = [ x(i:-1:max(i-N+1,1)).',zeros(1,max(N-i,0)) ];
    di = transpose([ d(i:-1:max(i-p(i)+1,1)).',zeros(1,max(p(i)-i,0)) ]);
    Yi = Xi*w;
    err= di-Yi;
    sqe = err.^2;
    UT = (mu*p(i)+2)*var/(2-mu);
    LT = (mu*(p(i)-1)+2)*var/(2-mu);
    if sqe(p(i)) > UT
        p(i+1) = min(p(i)+1,Pmax);
    elseif sqe(p(i))<= LT
        p(i+1) = max(p(i)-1,1);
    else
        p(i+1) = p(i);
    end
    w = w + mu*Xi'*inv(g*eye(p(i))+Xi*Xi')*(di-Yi);
    e_cont(i)= err(p(i));
end;

Rena Berman 2021-5-6

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Answer 1

Walter Roberson 2021-2-20

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在 MATLAB Online 中打开

It is legal to change the size of a matrix inside a loop, including being legal to let it grow one element at a time every iteration. However, it is more efficient if you can create the matrix at full size ahead of time. Sometimes much more efficient.

The problem with your code is that you do not initialize the variable Xi but you have

Xi(2:p(i),:) = Xi(1:p(i),:);

That requires that rows 1 to Pmax and all columns of Xi are initialized before the statement is executed -- but Xi is undefined here.

Also, the right hand side has p(i)-1+1 = p(i) rows, but the left hand side has p(i)-2+1 = p(i)-1 rows . This is a mismatch: you would be trying to store 4 rows of data into a location that only holds three rows.

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zahid fazal 2021-2-20

编辑：zahid fazal 2021-2-20

sir i tried to code for evolving order affine projection algorithm, which changes size of imput matrix (Xi) at every iteration acoording to p. what could be possible solution for it?

note: Xi is p rows N column matrix.