matlab+plot_fft
时间: 2024-02-03 17:04:05 浏览: 98
以下是两个使用MATLAB绘制FFT图像的例子:
1. 使用Ndata=136和Nfft=512的数据进行FFT绘图:
```matlab
Ndata = 136; % 数据个数
N = 512; % FFT所用的数据个数
n = 0:Ndata-1;
t = n/fs; % 时间序列
x = 0.5*sin(2*pi*15*t) + 2*sin(2*pi*40*t);
y = fft(x, N);
mag = abs(y);
f = (0:N-1)*fs/N; % 真实频率
subplot(2,2,4);
plot(f(1:N/2), mag(1:N/2)*2/N); % 绘出Nyquist频率之前的振幅
xlabel('频率/Hz');
ylabel('振幅');
title('Ndata=136 Nfft=512');
grid on;
```
2. 使用Ndata=32和Nfft=128的数据进行FFT绘图:
```matlab
Ndata = 32; % 数据个数
N = 128; % FFT采用的数据长度
n = 0:Ndata-1;
t = n/fs; % 时间序列
x = 0.5*sin(2*pi*15*t) + 2*sin(2*pi*40*t);
y = fft(x, N);
mag = abs(y);
f = (0:N-1)*fs/N; % 真实频率
subplot(2,2,2);
plot(f(1:N/2), mag(1:N/2)*2/N); % 绘出Nyquist频率之前的振幅
xlabel('频率/Hz');
ylabel('振幅');
title('Ndata=32 Nfft=128');
grid on;
```
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