# Debugging matrix dimensions error

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Deepayan Bhadra on 26 Nov 2019
Answered: James Tursa on 26 Nov 2019
I've a piece of code as follows:
data.r = zeros(Nr,N_experiments,end_sample-start_sample+1);
data.u = zeros(Nu,N_experiments,end_sample-start_sample+1);
data.y = zeros(Ny,N_experiments,end_sample-start_sample+1);
for k_exp = 1:N_experiments
for k_real = 1:N_realizations
for nr = 1:Nr
data.r(nr, k_exp,1:(end_sample-start_sample+1),k_real) = R((((k_exp-1)*N_realizations+(k_real-1))*(end_sample-start_sample+1)+1):(((k_exp-1)*N_realizations+k_real)*(end_sample-start_sample+1)),nr)';
end
for nu = 1:Nu
data.u(nu, k_exp,1:(end_sample-start_sample+1),k_real) = U((((k_exp-1)*N_realizations+(k_real-1))*(end_sample-start_sample+1)+1):(((k_exp-1)*N_realizations+k_real)*(end_sample-start_sample+1)),nu)';
end
for ny = 1:Nu
data.y(ny, k_exp,1:(end_sample-start_sample+1),k_real) = Y((((k_exp-1)*N_realizations+(k_real-1))*(end_sample-start_sample+1)+1):(((k_exp-1)*N_realizations+k_real)*(end_sample-start_sample+1)),ny)';
end
end
end
Dimensions as follows: Nr=2,Nu=2,Ny=2,N_experiments=2,N_realizations=1,start_sample=1441,end_sample=159951, R,U,Y=158511x2.
I get a 'Index exceeds matrix dimensions' error. This doesn't happen for k_exp = 1. I'm a little confused as some friends have used this same snippet and it has worked for them. What am I missing out?

James Tursa on 26 Nov 2019
How to debug:
Type the following at the MATLAB prompt:
dbstop if error
Then run your code. When the error occurs, the code will pause with all variables intact. Examine the variables on the line in question to see what the actual dimensions are. Then backtrack in your code to figure out why the dimensions or indexing are not what you expected.