Hi,
I understand that you are facing dimensionality error in your code.
It is possible that there is a mismatch in the dimensions of the variables you are working with in your mygfun function, specifically with the line
b(i) = y(tspan==state.time);
This suggests that y(tspan==state.time) is not returning a single element, which is causing the assignment error.
In order to debug and fix this issue, ensure that y(tspan==state.time) returns a single value. According to me, you can follow the approach as mentioned below to troubleshoot and resolve the problem:
- Ensure that 'state.time' is a single scalar value and that 'tspan' contains the time points you expect.
- Print or check the values of 'tspan' and 'state.time' to ensure they match up correctly.
- If y(tspan==state.time) returns multiple values, you might need to adjust your logic to ensure a single value is assigned.
You can refer to the following modified mygfun function code snippet to debug and potentially fix the issue.
function gcoeff = mygfun(~, state)
global y tspan
Da = 0.01;
[u_n, u_m] = size(state.u);
b = zeros(u_n, u_m);
tspan = 0:0.05:1;
for i = 1:u_m
% This is solving for one governing equation, hence one
% for loop and the notation u(i).
bfun = @(t,y) state.u(i).*(1-y) - y./2;
[t,y] = ode45(bfun, tspan, 0);
% Print state.time and check against tspan
disp(['state.time: ', num2str(state.time)]);
disp(['tspan: ', num2str(tspan)]);
% Find the index of the closest time point in tspan to state.time
[~, idx] = min(abs(tspan - state.time));
% Ensure that the index is valid and assign the corresponding value from y
if ~isempty(idx) && idx > 0 && idx <= length(y)
b(i) = y(idx);
else
error('No valid time point found in tspan for the given state.time.');
end
end
gcoeff = Da.*state.u.*(1-b)- b./2;
end
In the above code, wherever (tspan==state.time) does not hold true, the closest possible value will get assigned to b(i). This is necessary to avoid any floating-point precision issues because if 'state.time' and the values in 'tspan' are not exactly the same due to numerical precision, the comparison (tspan==state.time) may not return 'true' for any element, leading to an empty result.
Hope it helps!
Regards
Zuber
