### 在matlab程序中绘制图形时出错

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``````% let 'y' is a workspace file containg sampled data from DSO.
fs=2500;   %sampling freq
T=1/fs;     % sample time
L=2500;    % length of the signal
t=(0:L-1)*T;  %time vector
NFFT=2^nextpow2(L);   %next power of 2 from length of y.
%p = nextpow2(y) returns the smallest power of two that is greater than or equal to the absolute value of L.
%(That is, p that satisfies 2^p >= abs(L)).
%This function is useful for optimizing FFT operations, which are most efficient when sequence length is an exact power of two.
%If A is non-scalar, nextpow2 returns the smallest power of two greater than or equal to length(L).
Y=fft(y,NFFT)/L;
f=fs/2*linspace(0,1,NFFT/2);
% to plot signal-sided amplitude spectrum.
plot(f,2*abs(Y(1:NFFT/2)))
title('Single-sided amplitude spectrum of y(t)');
xlabel('Frequency (Hz');
ylabel('|Y(f)');
grid;
bar(f,2*abs(Y(1:NFFT/2)),'BarWidth',1)
``````

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``````% to plot signal-sided amplitude spectrum.
plot(f,2*abs(Y(1:NFFT/2))) % create a plot
title('Single-sided amplitude spectrum of y(t)'); % annotate it nicely
xlabel('Frequency (Hz');
ylabel('|Y(f)');
grid;
% throw away all that nice data and plot and plot over it with this:
bar(f,2*abs(Y(1:NFFT/2)),'BarWidth',1)
``````

``````figure;
% to plot signal-sided amplitude spectrum.
plot(f,2*abs(Y(1:NFFT/2)))
title('Single-sided amplitude spectrum of y(t)');
xlabel('Frequency (Hz');
ylabel('|Y(f)');
grid;
figure;
bar(f,2*abs(Y(1:NFFT/2)),'BarWidth',1)
``````