Inconsistent images of the same signal after FFT and DFT processing

Sine wave: “s = sin(((1:64)-1)*2*pi*w/100)” for various values of w. Inconsistency between DFT and FFT images occurs when w is equal to an integer multiple of 12.5. The images are consistent when w is other values.

FFfunction sw = dft(st)

% DFT - Discrete Fourier Transform

M = length(st);

N = M;

WN = exp(2*pi*1j/N);

% Main loop

for n=0:N-1

temp = 0;

for m=0:M-1

temp=temp+st(m+1)*WN^(m*n);

end

sw(n+1) = temp;

subplot(4,1,1); stem(real(sw)); title('Real');

subplot(4,1,2); stem(imag(sw)); title('Imag');

subplot(4,1,3); stem(abs(sw)); title('Abs');

subplot(4,1,4); stem(angle(sw)); title('Angle');

end

function swf = FFt(s)

swf=fft(s);

subplot(4,1,1); stem(real(swf)); title('Real');

subplot(4,1,2); stem(imag(swf)); title('Imag');

subplot(4,1,3); stem(abs(swf)); title('Abs');

subplot(4,1,4); stem(angle(swf)); title('Angle');

end