what is the error with my code

N = 4; 
x = [ 3 4 5 6 ]; 
for k = 0 : N-1
    for n=0:N-1
       sum = sum + x.*(exp(-1*1i*2*pi*k.*n/N));
    end
end
stem(sum)

Answer 1

[Adam Danz]

> what is the error with my code

The error is,

N = 4;
x = [ 3 4 5 6 ];
for k = 0 : N-1
    for n=0:N-1
        sum = sum + x.*(exp(-1*1i*2*pi*k.*n/N)); 
        %     ^^^ ERROR
    end

end

Error using sum
Not enough input arguments.

stem(sum)

What is causing the error (the question you intended to ask)?

sum() is a very commonly used Matlab function.

You're using it as a variable name but Matlab doesn't know it's a variable name because you haven't declared it as a variable by assiging a value to it.

Solution

Don't use sum as a variable name.

Answer 2

[Mahaveer Singh]

% give the initial value of sum.

% like sum=0 (initial vlue of sum)

N = 4;

x = [ 3 4 5 6 ];

sum=0;

for k = 0 : N-1

for n=0:N-1

sum = sum + x.*(exp(-1*1i*2*pi*k.*n/N));

end

end

stem(y)

[Adam Danz]

Even if this is within its own function workspace, I advise against using sum as a variable name.

1. It's a very commonly used Matlab function.
2. It makes the code more difficult to read because when people see sum they expected it to be the function.