index out of bounds because numel(v)=1.

I'm working with a for loop to recalculate the values of x and v but I'm getting an error for v(2) can some one explain what I'm doing wrong!

this is the code-data

    T=0.02;
    N=length(ag);
    t=0:T:(N-1)*T;
    a1 =-475.38 ;
    a2 = -0.5404;
    x0=0;
    v=0;

    for k=1:N;
        x(k)=x0+T*v
        v(k)=a1*x(k)+a2*v(k)-ag(k)

    end

below is the data and the code I'm using.

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T=0.02;
N=length(ag);
t=0:T:(N-1)*T;
a1 =-475.38 ;
a2 = -0.5404;
x0=0;
v=0;

for k=1:N;
    x(k)=x0+T*v
    v(k)=a1*x(k)+a2*v(k)-ag(k)

end

Answer 1

[Walter Roberson]

You initialize v=0 so that makes v length 1. In the first iteration of the for loop, k=1, you use v(1) to calculate a value that is assigned to v(1). On the second iteration of the for loop,, k=2, you try to use v(2) to calculate v(2) but v(2) does not exist yet.

Caution: if you did manage to create v(2) and so on, then your statement

x(k)=x0+T*v

would be using the vector v, and so would calculate a vector result and would attempt to store that vector into the single numeric array element x(k) . That is going to fail.

[Bob]

I think I got it now Thank you.

this is what I did.

for k=1:N;

x(k)=x0+T*v0;

x0=x(k)

v(k)=v0+T*(a1*x0+a2*v0-ag(k));

v0=v(k)

end