generating a matrix with 2 coordinates

m = input('Enter a number of row (m):'); % Number of rows
n = input('Enter a number of columns (n):'); % Number of Columns
M = randi(100,[m,n]) % It generates random Matrix with the size of m x n
min = inf;
max = 0;

for a = 1:m
    for b = 1:n
        if  M(a,b) < min
            min = M(a,b);
            mina = a;
            minb = b;
        end
        
        if M(a,b) > max
            max = M(a,b);
            maxa = a;
            maxb = b;
        end
    end
    
end
fprintf('Min is %d at:%d,%d\n',min,mina,minb);
fprintf('Max is %d at:%d,%d\n',max,maxa,maxb);

for c = mina:maxa
    for d = minb:maxb
        if M(c,d) >= 0
            M(c,d) = -M(c,d);
            
        end
    
    end  
    
end 

in this code i found the min and the max in the array but i have to generate a matrix with this M(mina,minb) and M(maxa,maxb). These coordinates should be the corners of the matrix.How can i do it can you help me ? By the way there shouldnt be any built in functions. Thanks

[Walter Roberson]

https://www.mathworks.com/matlabcentral/answers/38787-what-can-be-programmed-without-any-built-in-functions

[Umut Oskay]

do you know any way ?

[Walter Roberson]

I wrote that post. If I knew of any way to do anything meaningful in MATLAB without using a built-in function, I would have included it in that post.

[Umut Oskay]

Hmm okey. There should be some way to do it . In the previous part you said the same thing but somebody did it well.Thanks

[Walter Roberson]

Incorrect. James' solution violated the rules about not using built-in functions, and you should have rejected his solution. I responded there listing exactly the names of the built-in functions that were called. Do I need to link to their individual documentation pages to prove that they are functions?

https://www.mathworks.com/help/matlab/ref/subsref.html

Read it. It says explicitly that the function is called to implement indexing.

IN MATLAB IT IS IMPOSSIBLE TO INDEX WITHOUT USING THE FUNCTION NAMED subsref. subsref is a built in function. If your program contains even one subscript use, then it uses a built-in function, which violates the rules of the assignment.