Creating a matrix per iteration

Hello,

I'm trying to create a new matrix for each iteration of my loop. Here's the problem, I have to test 3 differential equations solvers, i.e. ode45, ode23, ode15s. I'd like to save the result of each loop in a matrix.

Here's the code :

for i=1:5
    for j=1:5
        options(i,j) = odeset ('RelTol',10^(-i),'AbsTol',10^(-j));
        [T1,X]=ode45(@odefunction,[0 5],[0 5],options(i,j));
        [T2,Y]=ode23(@odefunction,[0 5],[0 5],options(i,j));
        [T3,Z]=ode15s(@odefunction,[0 5],[0 5],options(i,j));
end

I don't know the size of the matrix since the result of each ode gives a different size.

Thank you.

Answer 1

[Geoff Hayes]

Martin - save your output to a cell array which allows for each element to be of a different type or size which is perfect for your example. For example, you could have one cell array where each element is a structure that has fields for X, Y, Z, T1, T2, and T3. Something like

 data = cell(5,5);

 for i=1:5
    for j=1:5
        options(i,j) = odeset ('RelTol',10^(-i),'AbsTol',10^(-j));
        [T1,X]=ode45(@odefunction,[0 5],[0 5],options(i,j));
        [T2,Y]=ode23(@odefunction,[0 5],[0 5],options(i,j));
        [T3,Z]=ode15s(@odefunction,[0 5],[0 5],options(i,j));

        data{i,j}.T1 = T1;
        data{i,j}.X  = X;
        data{i,j}.T2 = T2;
        data{i,j}.Y  = Y;
        data{i,j}.T3 = T3;
        data{i,j}.Z  = Z;
 end

Try the above and see what happens. As an aside, you may want to use indexing variables other than i and j which MATLAB uses to represent the imaginary number.

[Geoff Hayes]

Martin's answer moved here

Thank you very much, I thought I had to use the cell command but I didn't know how to use it properly. Your code works perfectly, this is exactly what I wanted.

By the way, thanks for the advice, I'll rename the two variables used for the loops.