title: Python plotting with for loop
body: <p>I am a newbie in python and plotting stuff. I was trying to generate a plot using the following script. The goal was to draw a plot of Q vs F for all values.  </p>
  
  <pre><code>from pylab import *
  
  n = 5
  D = 13
  B = 10
  
  x = linspace(-6.5, 6.5, 1000)
  y = 1/sqrt(2*pi)*exp(-(x)**2/2)
  
  for i in range(1,n):
      F = sum(y*cos(2*pi*i*x/D)*exp(-i**2*B/(4*D**2)))
      print F
  
  for j in range(1,n):
      Q = 2*pi*(j)/D
      print Q
  
  plt.plot(Q,F,'rx')
  plt.show()
  </code></pre>
  
  <p>When I am running the script, it plots only one data point instead of all. I am sure, I did some stupid mistake. Someone could pls help me out here? Thank you.</p>