plot(n, f(n))

[melvin13]

Hello,
I'm having a hard time understanding something:

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from pylab import * import numpy as np import numpy.fft as npft import scipy.io.wavfile as wavfile import math   fs_u1 , u1 = wavfile.read("u1.wav") #u1 is a numpy array of complex values   n= np.arange(0,u1.size)   def module(z): # returns the module of the complex z     a = z.real     b = z.imag     return math.sqrt(a**2+b**2)   def filtrage(M, y) : # should take an int M and a numpy array y, return a numpy array     ychap = np.fft.fft(y)     N = ychap.size     mask = np.ones(N)     coord = np.arange(M+1,N-M,1)     mask[coord]=0     yfiltchap = mask*ychap     yfilt = np.fft.ifft(yfiltchap)     yfilt = yfilt.real     return yfilt   def divisionEuclide(x): # should return the sum of the modules of all the complex value of the numpy array sent to it     sum = 0     for i in(n):         sum+= module(x[i])**2     return sum     plot(n, divisionEuclide(u1-filtrage(n,u1)))

returns the error:

Error:
File "...", line 29, in filtrage
    coord = np.arange(M+1,N-M,1)

ValueError: The truth value of an array with more than one element is ambiguous. Use a.any() or a.all()

I thought the "n" sent to filtrage() by "plot(n, divisionEuclide(u1-filtrage(n,u1)))" was a integer of the array n, not the array itself, since :

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n = np.arange(0,10)   def f(x):     return 2*x plot(n, f(n))

works just fine.
So why is the whole array sent to the function filtrage in the first example ? And how do I change that ?
I hope you can help me, thank you !

[Gribouillis]

In your working example with plot(n, f(n)) the function f() receives a whole array of integers, not a single integer.

[melvin13]

Thank you for answering !
I misunderstood the way plot() works then. But how would you plot divisionEuclide(u1-filtrage(n,u1)) in function of the values contained in n ?