How to store Values in a Loop?

for t=0:1:10
    L(t) = 3*cos(t);
    M(t) = diag([L 5*cos(t) 7*cos(t)]);
    K(t) = [12e5*cos(t) 18e5*cos(t) 34e5*cos(t);18e5*cos(t) 15e5*cos(t) 12e5*cos(t);13e5*cos(t) 12e5*cos(t) 22e5*cos(t)];
    [X,e] = polyeig(K, M)
    o = sqrt(e);
    fprintf('the freqeuncy is"%d" \n',o)
    writematrix(o,'hello/tt.xlsx','sheet',1,'range','A1:A30');
end

Hi, From the above code I am trying to store 10 time series in a single excel file but I can't able to do it and getting a error like "Array indices must be positive integers or logical values". Can anyone please help me in this.

Thank you in Advance.

[Walter Roberson]

for t=0:1:10
    L(t+1) = 3*cos(t);
    M(t+1) = diag([L 5*cos(t) 7*cos(t)]);
    K(t+1) = [12e5*cos(t) 18e5*cos(t) 34e5*cos(t);18e5*cos(t) 15e5*cos(t) 12e5*cos(t);13e5*cos(t) 12e5*cos(t) 22e5*cos(t)];
    [X,e] = polyeig(K, M)
    o = sqrt(e);
    fprintf('the freqeuncy is"%d" \n',o)
    writematrix(o,'hello/tt.xlsx','sheet',1,'range','A1:A30');
end

[naresh bhimchand]

But still I am getting error like "Unable to perform assignment because the indices on the left side are not compatible with the size of the right side".

[Walter Roberson]

Your L is increasing in length each iteration For each length of L, you diag() including all of L, so your M diagonal matrices are increasing in size each iteration. Your K matrix is not increasing in size each step. You ask to polyeig all of the K matrices and M matrices together. There are ways that all of the K and M matrices can be dropped into a single call, like polyeig(first_k, second_k, third_k, ..., first_m, second_m, third_m, ...) and your K matrices are all the same size, and your first M matrix is the same size as your K matrices, but your second M matrix is larger than the K matrices and the first M matrix, so by the second iteration you would be trying to polyeig() a series of matrices that included at least two different sizes, which is not permitted for polyeig.

Remember, if you expect M(t) to represent an entire matrix, then M without a subscript has to refer to all of the M matrices together, some-how.

[naresh bhimchand]

ok bro thank you very much

Answer 1

[David Hill]

for t=0:10
    L = 3*cos(t);
    M = diag([L 5*cos(t) 7*cos(t)]);
    K = [12e5*cos(t) 18e5*cos(t) 34e5*cos(t);18e5*cos(t) 15e5*cos(t) 12e5*cos(t);13e5*cos(t) 12e5*cos(t) 22e5*cos(t)];
    [X,e] = polyeig(K, M)%X is a 3x3 matrix, e is 3x1 vector
    o(:,t+1) = sqrt(e);%o is a 3x11 matrix when the loop finishes
end
writematrix(o,'hello/tt.xlsx','sheet',1,'range','A1:A30');

The only thing you are writing to file is the variable o; therefore it is the only thing needing to be in an array.

[naresh bhimchand]

Thanks, bro.But,for this in write matrix its only storing the last loop matrix values, I want to store all 10 time series loop values in a excel format.

[Walter Roberson]

If your o is ending up as 3x11 then it has all of the iterations in it.

Note that you are calculating 33 values not 30, because 0:10 is 11 iterations not 10; and that you are asking to write the 3x11 martrix into a 30x1 array. Perhaps you should change the 0:10 to 0:9 and perhaps you should writematrix o(:) instead of o

[naresh bhimchand]

I got it, bro.Thanks :)