NumPy 一維傅立葉轉換

1d_fft_demo.py

import numpy as np
import matplotlib.pyplot as plt

t = 2              # 取樣時間
sample_rate = 800  # 取樣率，每秒取幾個樣本

def signal(t, sample_rate):
    f = 10
    x = np.linspace(0, t, int(t * sample_rate), endpoint = False)
    return (np.sin(f * 2 * np.pi * x) +    
            np.sin(3 * f * 2 * np.pi * x) / 2 + 
            np.sin(4 * f * 2 * np.pi * x) / 5 +
            np.sin(8 * f * 2 * np.pi * x) / 3)

samples = signal(t, sample_rate)
sp = np.fft.fft(samples) 

freq = np.fft.fftfreq(samples.size, d = 1 / sample_rate)
amp = np.abs(sp)

ax = plt.gca()
ax.stem(freq, amp / np.max(amp))
ax.set_xlim([np.min(freq), np.max(freq)])
plt.show()