Assign a label to a point of a matrix in if statement

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MarshallSc 2021-6-1

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编辑： Stephen23 2021-6-2

Hi, I'm trying to assign a label (based on a category from a table) to each element of a 10*10 matrix in an if statement such that if the value is smaller or larger from a threshold, the corrosponding element gets assigned a certain category label with the index of the element so that it can be known which element it is . For example:

Kappa=rand(10,10);
KappaLong=rand(10,10);
KappaShort=rand(10,10);
for i=1:10
    for j=1:10
        if ((abs(Kappa(i,j)))/(abs(KappaLong(i,j)))<1) && ((abs(Kappa(i,j)))/(abs(KappaShort(i,j)))<1)
            Kappa(i,j)='Point is stable: Category 1 is assigned' %to show which element of the matrix is stable
        elseif ((abs(Kappa(i,j)))/(abs(KappaLong(i,j)))>1) && ((abs(Kappa(i,j)))/(abs(KappaShort(i,j)))>1)
            Kappa(i,j)='Point is unstable'
% (the code should continue after the elseif)
                 if abs(Kappalong)>abs(KappaShort)
                    ModKappa=abs(KappaLong)
                 else ModKappa=abs(KappaShort)
         end
     end
  end
end

I know the code above is not complete or correct, just wanted to provide an example about what I mean. Thank you in advance.

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MarshallSc 2021-6-1

Thanks for your reply Bob. Well, when I want to execute the code, I'll receive the following error in the line Kappa_j(i,j)='Point is stable: Category 1 is assigned' :

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 1-by-39.

I was wondering whether I'm writing this part incorrectly.

Stephen23 2021-6-2

编辑：Stephen23 2021-6-2

Note that storing lots of scalar numeric data in a cell array makes processing that data much slower and more complex. You should probably store the "status" string in a separate string array, and keep the numeric data in a numeric array.

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Answer 1

the cyclist 2021-6-1

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By default, Kappa_j is going to be a numeric array, and there cannot accept character input. Instead, you could define it as a cell array:

Kappa_j = cell(2,2); % Preallocate the cell array, but smaller to illustrate
Kappa_j{1,1} = 'Point is stable: Category 1 is assigned'
Kappa_j = 2×2 cell array
    {'Point is stable: Category 1 is assigned'}    {0×0 double}
    {0×0 double                               }    {0×0 double}

Notice the use of curly brackets to access the "inside" of the cell.