如何通过频谱图绘制时频图？

Question

I'm trying to plot time-frequency graph through a spectrogram. I want to make one line graph (x axis = time, y axis = frequency). I use Python and signal.stft function and get a spectrogram. I also calculate max frequency value in each time step. But I can't get an answer. What is the problem?

Answer 1

If I understood you correctly you want to plot a curve of max frequency on top of spectrogram? If yes you can simply call a second plot call of matplotlib after spectrogram. Something like this:

f, t, Zxx = signal.stft(x, fs, nperseg=1000)
max_f = np.argmax(data, axis=1)  # data has shape (time x frequency)
plt.pcolormesh(t, f, np.abs(Zxx), vmin=0, vmax=amp)
plt.plot(np.arange(max_f.shape[0]), max_f)
plt.ylabel('Frequency [Hz]')
plt.xlabel('Time [sec]')
plt.show()