DWT导出时频图MATLAB代码

以下是DWT导出时频图MATLAB代码示例：

% Load signal
load('ecg.mat'); % Load ECG signal
Fs = 1000; % Sampling frequency
t = 0:1/Fs:(length(ecg)-1)/Fs; % Time vector
N = length(ecg); % Signal length

% DWT
wname = 'db4'; % Wavelet name
level = 5; % Number of decomposition levels
[C, L] = wavedec(ecg, level, wname); % DWT coefficients and lengths

% Time-frequency analysis using spectrogram
win = 256; % Window length for spectrogram
noverlap = 128; % Window overlap for spectrogram
nfft = 1024; % FFT length for spectrogram
figure;
spectrogram(ecg, win, noverlap, nfft, Fs, 'yaxis');
title('Original signal spectrogram');

figure;
for i=1:level+1 % Plot DWT coefficients at each level
    if i == 1 % Approximation coefficients
        D = appcoef(C, L, wname, level);
        titlestr = 'Approximation coefficients spectrogram';
    else % Detail coefficients
        D = detcoef(C, L, i-1);
        titlestr = ['Detail coefficients level ', num2str(i-1), ' spectrogram'];
    end
    spectrogram(D, win, noverlap, nfft, Fs, 'yaxis');
    title(titlestr);
end

该代码首先加载一个ECG信号，然后对其进行DWT分解，使用`spectrogram`函数将原始信号和每个DWT系数的时频图绘制出来。函数`spectrogram`接受多个参数，包括信号、窗口长度、窗口重叠、FFT长度和采样频率。结果显示了原始信号和每个DWT系数的时频图。