How to fill array with previous values?

Question

George Francis 2018-6-11

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回答： George Francis 2018-6-11

Hello guys I have data which contains 2 columns and 600 rows. It basically contains inputs u and outputs y. And my question is how can I fill array 3x1 as follows:

z=[-u(n)-2*u(n-1)-u(n-2);y(n-2)-y(n-1);y(n)-y(n-1)];

I know that I have to make loop but my loop which is below isn't correct and I don't know how to fix it. So can you please help me?

N=length(y);
for n=1:N
    for i=1:2
        W(i) = y(n-i);          %output
    end
    for i=1:2
        V(i) = u(n-i+1);        %input
    end
    z = [V';W'];
end

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Answer 1

KSSV 2018-6-11

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https://ww2.mathworks.cn/matlabcentral/answers/405026-how-to-fill-array-with-previous-values#answer_324103

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A = rand(600,2) ;   % some random data 
u = A(:,1) ; y = A(:,2) ;
n = 1:600 ;
z = zeros(600,3) ;
for n = 3:600
    z(n,:) = [-u(n)-2*u(n-1)-u(n-2) y(n-2)-y(n-1) y(n)-y(n-1)];
end
z(1:2,:) = [] ;

Note, the above can be achieved without loop also.

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George Francis 2018-6-11

the problem is z has to be array 3x1 when I tried your version z is 598x3.

KSSV 2018-6-11

As z is inside loop, every loop value has been saved..

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Answer 2

George Francis 2018-6-11

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https://ww2.mathworks.cn/matlabcentral/answers/405026-how-to-fill-array-with-previous-values#answer_324123

在 MATLAB Online 中打开

I'm making some other calculations from z so z has to be 3x1 in that loop. I actually tried something see code below. But I don't know if it's working correctly. I mean it works but I don't know if that is solution which I was looking for.

delta = 0.002;
sigma=1;
lamda=1;
C = sigma*eye(3);  
P = [1;1;1];
N=length(y);
for n = 4:N
    for i=1:3
        W(i) = y(n-i);
      end
      y_n=W(1,1);
      yn_1=W(1,2);
      yn_2=W(1,3);
      for i=1:3
          D(i) = u(n-i);
      end
      u_n=D(1,1);
      un_1=D(1,2);
      un_2=D(1,3);
      z = [-u_n-2*un_1-un_2;yn_2-yn_1;y_n-yn_1];
      rk=-4*delta^2*yn_1;
      C = (C - ( (C*z*z'*C)/( lamda+(z'*C*z) ) ))/lamda;
  P = P + C*z*(rk - (z'*P))/(lamda+(z'*C*z));
  end