title: Why am I geting this error? AttributeError: 'module' object has no attribute 'periodogram'
body: <p>I have copied the following lines </p>
  
  <pre><code>from scipy import signal
  import matplotlib.pyplot as plt
  import numpy as np
  
  fs = 10e3
  N = 1e5
  amp = 2*np.sqrt(2)
  freq = 1234.0
  noise_power = 0.001 * fs / 2
  time = np.arange(N) / fs
  x = amp*np.sin(2*np.pi*freq*time)
  x += np.random.normal(scale=np.sqrt(noise_power), size=time.shape)
  # Compute and plot the power spectral density.
  
  f, Pxx_den = signal.periodogram(x, fs)
  plt.semilogy(f, Pxx_den)
  plt.xlabel('frequency [Hz]')
  plt.ylabel('PSD [V**2/Hz]')
  plt.show()
  </code></pre>
  
  <p>from **<a href="http://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.periodogram.html#scipy.signal.periodogram" rel="nofollow">http://docs.scipy.org/doc/scipy/reference/generated/scipy.signal.periodogram.html#scipy.signal.periodogram</a>  but when I try to run the code I'm getting this error: </p>
  
  <pre><code>f, Pxx_den = signal.periodogram(x, fs)
  AttributeError: 'module' object has no attribute 'periodogram'
  </code></pre>
  
  <p>I'm using Scipy version 0.12
  Thank your for your help.
  Kind Regards.
  Ivo</p>