how to iterate cell array?

Question

Majid 2023-2-26

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1918940-how-to-iterate-cell-array

评论： Rik 2023-3-4

在 MATLAB Online 中打开

hello !

i have a cell array N1 (100x1),attached here, i want to do 51 iteration for each element of N1(each matrix).

knowing that N1 was saved and i just load it.

i tried with different method but always the same error

 for i = 1:51
     i = i+1 
for itr = 1:100   %number of iteration is the size of my cell array
N = all_N1{i,itr};  % here is error " Index in position 2 exceeds array bounds. Index must not exceed 1."
%...............code
end
 end
 

any help is appreciated!

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Answer 1

Walter Roberson 2023-2-26

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链接

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https://ww2.mathworks.cn/matlabcentral/answers/1918940-how-to-iterate-cell-array#answer_1180010

You say that N1 is 100 x 1.

You have iter = 1:100 so on the second round, iter will become 2.

You have all_N1{i,iter} but iter has become 2 on the second iteration. But your cell array is 100 x 1 so there is no second column. Not unless you assigned into all_N1{:,2} inside the for i loop.

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Majid 2023-2-26

@Walter Roberson N1 is already saved , i'm searching for a solution that makes me execute each matrix of N1 for 51 iterations

Walter Roberson 2023-2-26

N1 is already saved as 100 x 1. When your for itr becomes 2, you attempt to access all_N1{i,iter} which would be all_N1{i,2} . If N is the same thing as all_N1 then you have a problem.

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Answer 2

VBBV 2023-2-26

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1918940-how-to-iterate-cell-array#answer_1180045

编辑：VBBV 2023-2-26

在 MATLAB Online 中打开

 for i = 1:51
  for itr = 1:100   %number of iteration is the size of my cell array
  N = all_N1{itr,i};  % switch position of indices. 
  end
end

As you say, N1 is of size 100x1, you need to switch the position of indices in the inner for loop as above. Also, you don't require to increment the outer for loop index, as this will cause the index to exceed out of bounds i.e. > 51 end

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VBBV 2023-3-3

在 MATLAB Online 中打开

clear all % add this at the beginning of code
M = {rand(100,1)}  % some data 
M = 1×1 cell array
    {100×1 double}
N1 = repmat(M,100,1) %each N1 is 100 x 1 
N1 = 100×1 cell array
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
    {100×1 double}
all_N1 = repmat(N1,1,51)  % assuming all N1 
all_N1 = 100×51 cell array
    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}
    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}    {100×1 double}
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for i = 1:51   % 
  for itr = 1:100   %number of iteration is the size of my cell array
     N = all_N1{itr,i};  %       
  end
end
N
N = 100×1
    0.7226
    0.0332
    0.8978
    0.6621
    0.7076
    0.5424
    0.5816
    0.2112
    0.2799
    0.7556

Its unlikely you would get such error, Can you check whether you cleared all variables in your workspace ?each time you begin to run code, otherwise the workspace variables get populated and exceed the array dimensions,

Rik 2023-3-4

Why suggest clear all? Using a function would also provide a clean slate.

Note that clear or clearvars should be preferred, as clear all clears much more. It is almost equivalent to restarting Matlab every time you run the code.

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Answer 3

Torsten 2023-2-26

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链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1918940-how-to-iterate-cell-array#answer_1180360

在 MATLAB Online 中打开

all_N1 = cell(51,1);
% Generate 100 matrices of size 20x20 and save them in cell array
for i = 1:100
  all_N1{i} = rand(20);
end
% Use the matrices in iterations
for i = 1:100
  M = all_N1{i};
  for iter = 1:51
    % do something with the matrix M
  end
end

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Rik 2023-3-3

在 MATLAB Online 中打开

So you didn't do what I suggested. Why exactly didn't you do that? You should have implemented it something like I did below.

% Load data from mat file
step = load('all_N1.mat');
all_N1 = step.all_N1;
% Prepare output parameters
MyResult = cell(1,numel(all_N1));
fval = cell(1,numel(all_N1));
for iter = 1:numel(all_N1)
    for f_in = 0:50
        i = f_in+1;
        % Run solver
        [MyResult{i,iter},fval{i,iter}, exitflag] = YourCustomFunction(all_N1{iter},f_in);
        
        % Overwrite fval when solver fails.
        if exitflag<=0
            fval{i,iter}=-inf;
        end
    end
end
function [MyResult,fval,exitflag] = YourCustomFunction(N,f_in)
S = optimvar("S",[M,1],"Type","integer","LowerBound",0,"UpperBound",1);
obj = fcn2optimexpr(  @Objective_function   ,S);
prob = optimproblem('ObjectiveSense','max');
prob.Objective = obj ;
constr1 = S <= Q./sum(fcn2optimexpr(  @Myconstraint1, q_int),2 );
constr2 =  cumsum(S.*(sum(Energy_Pr,2))) <= E_max(1)-E_prop;
prob.Constraints.constr1 = constr1;
prob.Constraints.constr2 = constr2;
[MyResult,fval, exitflag] = solve(prob);
end

Now you need to show me where exactly you're using f_in (or even N). I only see M, along with some undefined variables and functions you haven't shared.

Do you see how this helps defining the problem? Do you also notice how the part with the fewest comments is the part that is causing the issue? That should tell you something.

Rik 2023-3-3

I'm sorry, I'm out. I can't help you if you refuse to follow my advice for troubleshooting.

I hope fo you someone else will be able to pick up this thread, but I'm out.

If you change your mind you can attach the relevant m files and show your implementation of YourCustomFunction.

Torsten 2023-3-3

编辑：Torsten 2023-3-3

@Majid

You have been working on this problem for months now.

In the meantime, did you spend the 2 hours to pass the MATLAB tutorial ?

https://matlabacademy.mathworks.com/details/matlab-onramp/gettingstarted

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how to iterate cell array?

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how to iterate cell array?

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