Numpy.fft/Numpy.ffrfreq/Numpy.ifft

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Numpy FFT Example

@2018.12.11

 

Summary python numpy signal fft 티스토리

 

%matplotlib inline

import numpy as np

import matplotlib.pyplot as plt

 

#Sin Signal Class

class SinSample():

def __init__(self, **kwargs):

self.amp = kwargs.get('amp',1)

self.time = kwargs.get('time',t)

self.freq = kwargs.get('freq',3)

self.sample = np.sin(2*np.pi*self.freq*self.time)

 

def calSignal(self, freq):

return np.sin(2*np.pi*freq*self.time)

def addSample(self, freq):

self.sample = self.sample + (self.calSignal(freq))

#Init

Fs = 1000#1KHz

Ts = 1/Fs

t = np.arange(0.0, 1.0, Ts)

#Make Signal

Mysample = SinSample(amp=1, time=t, freq=3)

Mysample.addSample(50)

Mysample.addSample(100)

#Plot Signal

plt.figure(figsize=(12,5))

plt.plot(t, Mysample.sample)

plt.xlabel('Time(s)')

plt.title('Test Signal in Continuous')

plt.grid(True)

plt.show()

 

 

Y = np.fft.fft(Mysample.sample)

freq = np.fft.fftfreq(len(Y), d=Ts)

 

plt.figure(figsize=(12,5))

plt.plot(freq, np.abs(Y), 'r')

plt.xlabel('Freq (Hz)')

plt.ylabel('|Y(freq)|')

plt.grid(True)

 

###Delete 3hz signal don't use ifft ==> Error###

#check fft.freq function index -> not continuous

###############################################

Y = np.fft.fft(Mysample.sample)

freq = np.fft.fftfreq(len(Y), d=Ts)

 

#target hz

fg = 3

 

for i in range(0, len(Y)):

Y[i] *= (1 if abs(freq[i]) > fg else 0)

filterd_Y = np.fft.ifft(no_shift_Y)

plt.figure(figsize=(12,5))

plt.plot(freq, filterd_Y)

 

###Delete 3hz signal use ifft###

Y = np.fft.fft(Mysample.sample)

freq = np.fft.fftfreq(len(Y), d=Ts)

 

#shift x index (freq)

freq = np.fft.fftshift(freq)

 

#target hz

fg = 3

 

for i in range(0, len(Y)):

Y[i] *= (1 if abs(freq[i]) > fg else 0)

 

filterd_Y = np.fft.ifft(no_shift_Y)

plt.figure(figsize=(12,5))

plt.plot(freq, filterd_Y)

 

###Get FTT & Plot###

Y = np.fft.fft(filterd_Y)

freq = np.fft.fftfreq(len(f_Y), d=Ts)

 

plt.figure(figsize=(12,5))

plt.plot(freq, np.abs(f_Y), 'r')

plt.xlabel('Freq (Hz)')

plt.ylabel('|Y(freq)|')

plt.grid(True)

 

 

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코드

https://github.com/LazyerIJ/ECG_Analysis/blob/master/study/Numpy_fft_example.ipynb