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plotSpectrum.py
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plotSpectrum.py
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# -*- coding: utf-8 -*-
"""
Created on Fri Nov 08 15:19:22 2013
@author: rarossi
"""
from numpy import sin, pi
from pylab import plot, show, xlabel, ylabel, subplot, xlim
from scipy import fft, arange
def plotSpectrum(y,Fs,cutoff):
"""
Plots a Single-Sided Amplitude Spectrum of y(t)
"""
n = len(y) # length of the signal
k = arange(n)
T = n/Fs
frq = k/T # two sides frequency range
frq = frq[range(n/2)] # one side frequency range
Y = fft(y)/n # fft computing and normalization
Y = Y[range(n/2)]
plot(frq,abs(Y),'r') # plotting the spectrum
xlabel('Freq (Hz)')
ylabel('|Y(freq)|')
xlim(0,cutoff)
##############################################################################
Fs = 150.0; # sampling rate
Ts = 1.0/Fs; # sampling interval
t = arange(0,1,Ts) # time vector
ff = 5; # frequency of the signal
y = sin(2*pi*ff*t)
subplot(2,1,1)
plot(t,y)
xlabel('Time')
ylabel('Amplitude')
subplot(2,1,2)
plotSpectrum(y,Fs,10)
show()