There is an error in line 3. I can't figure out what the error is. Please help me find out.

Write a function called halfsum that takes as input a matrix and computes the sum of the elements in the diagonal and are to the right of it. The diagonal is defined as the set of those elements whose column and row indexes are the same. In other words, the function adds up to the element in the upper triangular part of the matrix. The name of the output argument is summa.

For example,

A = 
     1    2    3
     4    5    6
     7    8    9

The function would return 26 (1 + 5 + 9 + 2 + 3 + 6 = 26)

This is my code for the function;

function summa = halfsum(A)

[x, y] = size(A);

if x == y
    summa = 0;
    for n = 1:y
        summa = summa + sum(A(n, n:y));
    end
    
elseif x ~= y
    if x > y
    summa = 0;
    for n = 1:y
        summa = summa + sum(A(n, n:y));
    end
    
    elseif x < y
        summa = 0;
        for n = 1:x
            summa = summa + sum(A(n, n:y));
        end
        
    end
    
end

When I was debugging, MATLAB showed error in line 3. My code works fine but I don't know what's the error in line 3.

[Vignesh Murugavel]

what was the error message?

I ran your code in my system and i get the proper output : 26

[Pere Garau Burguera]

Hi Swetha,

You are missing an

end

at the bottom, to close the function.

You can also use the triu function, which returns the upper triangular part,

summa = sum(triu(A),'all');

Thanks,

Pere

[Walter Roberson]

Using end to close a function is not always required.

You must use end for the following cases:

• some other function in the file uses end matching its function declaration
• you are using nested functions
• you are creating a method of a classdef
• you are defining a function inside a script
• you want the semantics of creating a static workspace (which can be more efficient)

In the case of a single function that is the only function in it file with no script before it, then you only need the end if you want static workspace.

Using end is generally a good idea (though it can complicate debugging), but in the context of the posted user code, it is not required.

[Swetha Balaji Rao]

@Vignesh Murugavel I get the error saying 'not enough input arguments.'

Answer 1

[KSSV]

A = [ 1    2    3
     4    5    6
     7    8    9] ;
B = triu(A) 

B = 3×3

1 2 3 0 5 6 0 0 9

iwant = sum(B(:))

iwant = 26

[KSSV]

The given function too has no error. It works fine.

A = [1    2    3
    4    5    6
    7    8    9] ;

[x, y] = size(A);

if x == y
    summa = 0;
    for n = 1:y
        summa = summa + sum(A(n, n:y));
    end
    
elseif x ~= y
    if x > y
        summa = 0;
        for n = 1:y
            summa = summa + sum(A(n, n:y));
        end
        
    elseif x < y
        summa = 0;
        for n = 1:x
            summa = summa + sum(A(n, n:y));
        end
        
    end
end
summa    

summa = 26

If you are getting any specific error. Show us the error here.

Answer 2

[Walter Roberson]

You tried to run the function without passing any matrix to it, and matlab complained that it could not find any input being passed to it.

When a function requires parameters then you cannot just press the green Run button, and you cannot just give the name of the function by itself to run the function.

[Swetha Balaji Rao]

Then how can I debug the code? By giving a random matrix as an input and run the function??

[Walter Roberson]

A = [     1    2    3
     4    5    6
     7    8    9]
halfsum(A)