my graph looks weird

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Sachini Perera
Sachini Perera 2021-4-16
评论： Sachini Perera 2021-4-16
Hi,
My code is below and the answer i got also is below. But it looks weird with a lot of areas shaded. I want to remove the shaded part and make it so that only the lines are shown. How do i do this ?
fs = 200;
ts = 1/fs;
t = 0:ts:5;
z2 = 8*cos(30*pi*t+pi/3)+6*sin(50*pi*t-pi/3)+8*cos(70*pi*t-pi/4);
Y = fft(z2);
L = length(Y);
P2 = Y/L;
P1 = P2(1:L/2+1);
P1(2:end-1) = 2*P1(2:end-1);
f = fs*(0:(L/2))/L;
figure;
subplot(221)
stem(f,abs(P1),'linewidth',0.5);grid on; xlim([-40 40]);
title('Single-Sided Amplitude Spectrum of z_2(t)')
xlabel('f (Hz)');ylabel('|P1(f)|');
subplot(222)
stem(f,angle(P1)*57.3,'linewidth',0.5);grid on; xlim([-40 40]);
title('Single-Sided Phase Spectrum of z_2(t)')
xlabel('f (Hz)');ylabel('Degrees');
N = nextpow2(length(z2));
X = fftshift(fft(z2,2^N));
X = 2* X / length(z2);
k = -(length(X)-1)/2:1:length(X)/2;
f = k/length(X) * fs;
subplot(223);
stem(f,abs(X),'linewidth',0.5);grid;
xlabel('Frequency in Hz');
ylabel('Amplitude');xlim([-40 40]);
title('Double sided Magnitude spectrum of z_2(t)');
subplot(224);
stem(f,angle(X)*57.3,'linewidth',0.5);grid;
xlabel('Frequency in Hz');
ylabel('Amplitude');xlim([-40 40]);
title('Double sided Phase spectrum of z_2(t)');

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采纳的回答

Jan
Jan 2021-4-16
Maybe you want to remove the markers?
stem(f,angle(X)*57.3,'linewidth',0.5, 'Marker', 'none');
If you want something else, explain, what "only the lines are shown" means.
  1 个评论
Sachini Perera
Sachini Perera 2021-4-16
sorry for the poor explanation. When i meant only lines i only wants to show the important frequency components. For example, in the first subplot i only wants to show the 3 points that is has a higher amplitude than others.

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