Error using plot Vectors must be the same length

Question

Ha 2023-3-22

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1933695-error-using-plot-vectors-must-be-the-same-length

评论： Matt J 2023-3-22

在 MATLAB Online 中打开

% Define time range

t = -0.2:0.0001:0.2;

% Calculate signal s(t)

s = cos(2*pi*10*t).*cos(27*pi*200*t);

% Plot s(t)

figure(1);

plot(t, s);

xlabel('Time (s)');

ylabel('Amplitude');

title('AM Modulated Signal s(t)');

% Calculate Fourier transform of s(t)

Fs = 10000; % Sampling frequency

S = fftshift(fft(s))/length(s);

size(S)

ans = 1×2

1 4001

f = (-Fs/2:Fs/2-1)/length(s);

size(f)

ans = 1×2

1 10000

% Plot two-sided spectrum of S(f)

figure(2);

plot(f, abs(S));

Error using plot
Vectors must be the same length.

xlabel('Frequency (Hz)');

ylabel('Magnitude');

title('Two-Sided Spectrum of S(f)');

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Answer 1

Torsten 2023-3-22

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/1933695-error-using-plot-vectors-must-be-the-same-length#answer_1198765

移动：Matt J 2023-3-22

As you can see above, S and f have a different number of elements. So they cannot be plotted against each other.

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Ha 2023-3-22

I didn't understand what you mean..but what is wrong with the code? .. As for S.f, they have the same number of elements as shown in the code. Can the problem be solved?

Matt J 2023-3-22

在 MATLAB Online 中打开

As for S.f, they have the same number of elements as shown in the code.

It is puzzling that you think so. Running the code clearly shows that length(S)=4001 while length(f)=10000

% Define time range
t = -0.2:0.0001:0.2;
% Calculate signal s(t)
s = cos(2*pi*10*t).*cos(27*pi*200*t);
% Calculate Fourier transform of s(t)
Fs = 10000; % Sampling frequency
S = fftshift(fft(s))/length(s);
f = (-Fs/2:Fs/2-1)/length(s);
length(S)
ans = 4001
length(f)
ans = 10000