MATLAB Answers


How to store Values in a Loop?

Asked by naresh bhimchand on 11 Nov 2019 at 9:46
Latest activity Commented on by naresh bhimchand on 12 Nov 2019 at 2:39
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)
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.


Show 1 older comment
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
on 12 Nov 2019 at 1:04
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.
ok bro thank you very much

Sign in to comment.

1 Answer

Answer by David Hill on 12 Nov 2019 at 1:21
 Accepted Answer

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


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
on 12 Nov 2019 at 2:34
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
I got it, bro.Thanks :)

Sign in to comment.