how to find the position of in the matrix without using the neither find nor built in functions.

i have a matrix with the size of m x n . I found the min and max with the multiple for loops in the matrix without using any built in function . But i cannot find the position of them. Can you help me to find the position without using any built in function

[Matt J]

Perhaps. You should show the code that you have, though, so that the appropriate modifications canbe recommended.

[Umut Oskay]

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);   
        end
        
        if M(a,b) > max
            max = M(a,b);
        end
    end
    
end
fprintf('Min is %d at:\n',min);
fprintf('Max is %d at:\n',max);

[Umut Oskay]

in this case i need to find and display where the max and min are

[Walter Roberson]

This task cannot be done.

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

[Umut Oskay]

why

[Umut Oskay]

he did

[Walter Roberson]

Read my link; I explained why the task cannot be done.

Answer 1

[James Tursa]

Just add variables to keep track of the locations. E.g.,

        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

P.S. You should use variable names other than min and max, since those are existing MATLAB fuction names.

[Umut Oskay]

it works thankss . But i wantto know how did you think that it will give the true answer?

[James Tursa]

You also need to change:

• Initial max value from 0 to -inf
• The < test to <=
• The > test to >=

The last two changes are just to ensure that you always get the indexing results.

[Walter Roberson]

Unfortunately this code uses the built-in functions lt() and gt() and subsref()

In MATLAB, it is not possible to index into an array without using the built-in function subsref(), and that means that the overall task of finding the minimum and maximum of the array cannot be done without using any built-in functions.

Answer 2

[David Goodmanson]

Hi Umut,

all you need do is use a couple of 1x2 arrays to store a and and b when you find them

When inside the for loops when you find a new max,

maxM = M(a,b);
indmax = [a b];

and similarly for min. I changed max to maxM because max is already a builit-in Matlab function and you will cause yourself problems if you use it as a variable name. Same for min.

[Umut Oskay]

Thanks