How do i start my code over if i'm doing data validation?

I'm doing data validation within my code for homework. I'm typing a code that determines if a matrix is a magic-square. On a requirement sum of rows and cols must be equal but if they're not I'm supposed to ask user if they would like to try again. And if so, The matrix they entered needs to go through the entire code again for other data validation checks.

Answer 1

[Iddo Weiner]

Wouldn't the sum of rows always equal the sum of cols in any matrix? See this link for discussion on determining whether a matrix is magic or not:

https://www.mathworks.com/matlabcentral/newsreader/view_thread/262795

Anyway, here's a code that technically does what you ask. When you use rand() as input it will sometimes fail to recognize that the sum of rows and cols is equal becasue of the way MATLAB handles floating point variables:

function out = is_magic(matrix)
while true
    if sum(sum(matrix)) == sum(sum(matrix,2))
        out = 1;
        break
    else
        while true
            ANS = input('this matrix wasn''t magic. Would you like to try again? Y/N ','s');
            if strcmpi(ANS,'Y')
                matrix = input('insert new matrix:');
                break
            elseif strcmpi(ANS,'N')
                out = 0;
                return
            else
                disp('invalid answer')
            end
        end
    end
end

Here's a usage example:

>> is_magic(rand(3,4))
this matrix wasn't magic. Would you like to try again? Y/N Y
insert new matrix:magic(5)

ans =

       1

>> is_magic(rand(3,4))
this matrix wasn't magic. Would you like to try again? Y/N N

ans =

       0