I'm getting this error as shown below

The code

function [Xk] = DFT(xn)

N = length(xn);     %frame size
Xk = zeros(1,N);   %array size xn

            %DFT Algorithom 
 for k = 0:(N-1)
    n = 0:(N-1);
    Xk(k+1) = sum(xn(n+1).*exp((-1i*2*pi*k*n)/N));
   
  end
Xk = abs(Xk);
end

The error

The left-hand side has been constrained to be non-complex, but the right-hand side is complex. To correct this problem, make the right-hand side real using the function REAL, or change the initial assignment to the left-hand side variable to be a complex value using the COMPLEX function.

Please Help

Answer 1

[Walter Roberson]

function [Xkr] = DFT(xn)
N = length(xn);     %frame size
Xk = complex(zeros(1,N));   %array size xn
Xkr = zeros(1,N);
          %DFT Algorithom 
for k = 0:(N-1)
  n = 0:(N-1);
  Xk(k+1) = sum(xn(n+1).*exp((-1i*2*pi*k*n)/N));

end
Xkr = abs(Xk);
end

[Walter Roberson]

I am not sure why you are taking abs(): discrete fourier transform of real data always returns complex values unless the phases are all 0.

[Sean]

cause I thought it might fix the error since my testbench doesnt have imaginary values

[Walter Roberson]

I think you should code

function [Xk] = DFT(xn)

    N = length(xn);     %frame size
    Xk = complex(zeros(1,N));   %array size xn

    n = 0:(N-1);
    
    %DFT Algorithom 
    for k = 0:(N-1)
        Xk(k+1) = sum(xn(n+1).*exp((-1i*2*pi*k*n)/N));
    end
end

but that each place you call this function, you should code as expecting a complex result. Which you can take the abs() or real() or imag() part of, as appropriate.