问调整MATLAB fft的频率和幅值轴

EN

    N = 1000; % number of samples 
n = (0:N-1)'; % generate a vector n for x[n]
Fs_normal = 36621.09375;
%generate a signal in pass-band, N samples and simulate filter
f0 = 1000; % set 1000 Hz 
x= sin(2*pi*f0*n/Fs_normal); % input signal
figure(3);
stem(x),title('sinus wave with 1000 Hz (n)'),grid;
figure(4);
plot(abs(fft(x))),grid,title('FFT of sin wave with 1000 Hz  frequency');