title: IndexError: index out of bounds
body: <p>I am new to Python and appreciate any constructive feedback.
  My task is to solve a PDE using ODEINT where my spatial grid is defined as follows:</p>
  
  <pre><code>L = [8.0, 4.0, 8.0]   # Lenght of spatial zones 
  dN = 1.0e2            # Number of grid points
  N = [int(l*dN) for l in L] # Gives number of grid points over each spatial zone
  </code></pre>
  
  <p>By using the ODEINT function believe I must define an array of zeros for my solution, and an array of time points. I am struggling to find out how I write the correct size for the array's. I have tried:</p>
  
  <pre><code>dydt = np.zeros(shape=N) # For solution
  t = np.linspace(0, 2, 2000) # for time
  </code></pre>
  
  <h2>But that gives me the error message:</h2>
  
  <p>IndexError                                Traceback (most recent call last)
   in ()
       70 t = np.linspace(0, 2, lN)
       71 
  ---> 72 U = odeint(numeric, y0, t, args=(h, D1, D2, N))
       73 
       74 Fexit = U/Np</p>
  
  <p>/Users/severinlangeberg/anaconda/lib/python3.5/site-packages/scipy/integrate/odepack.py in odeint(func, y0, t, args, Dfun, col_deriv, full_output, ml, mu, rtol, atol, tcrit, h0, hmax, hmin, ixpr, mxstep, mxhnil, mxordn, mxords, printmessg)
      213     output = _odepack.odeint(func, y0, t, args, Dfun, col_deriv, ml, mu,
      214                              full_output, rtol, atol, tcrit, h0, hmax, hmin,
  --> 215                              ixpr, mxstep, mxhnil, mxordn, mxords)
      216     if output[-1] &lt; 0:
      217         warning_msg = _msgs[output[-1]] + " Run with full_output = 1 to get quantitative information."</p>
  
  <p> in numeric(y, t, h, D1, D2, N)
       39 
       40     for i in [N[0] + 1]: # 800 = special 2, must be from begining of N[1]
  ---> 41         dydt[i] = D2 * (-3*y[i] + 4*y[i + 1] - y[i + 2] / h**2) # pluss
       42 
       43     for i in range (N[0] + 2, N[0] + N[1] - 2): # from 801 to 1197, or 2 to 397</p>
  
  <p>IndexError: index 801 is out of bounds for axis 0 with size 800</p>
  
  <pre><code>Which seems to come from my loops:
  # ODE setup
  def numeric(y, t, h, D1, D2, N):
  
      dydt = np.zeros((N))
  
      # End grid points
      dydt[0] = 0
      dydt[-1] = 0
  
  
      # Inner grid points
      for i in range (1, N[0] - 2): # 1 to 797
          dydt[i] = D1 * (y[i - 1] - 2*y[i]+ y[i + 1]) / h**2 # range i = j - 1
  
      for i in [N[0] - 2]: # 798 = special 1
          dydt[i] =  D1 * (-3*y[i] - 4*y[i - 1] + y[i - 2]) / h**2 # minus
  
      for i in [N[0] - 1]: # 799 = unknown, and last index in N[0]
          dydt[i] = ((D1*(-3*y[i] + 4*y[i + 1] - y[i + 2])) - (D2*(-3*y[i] - 4*y[i - 1] + y[i - 2])))
  
      for i in [N[0] + 1]: # 800 = special 2, must be from begining of N[1]
          dydt[i] = D2 * (-3*y[i] + 4*y[i + 1] - y[i + 2] / h**2) # pluss
  
      for i in range (N[0] + 2, N[0] + N[1] - 2): # from 801 to 1197, or 2 to 397
          dydt[i] = D2 * (y[i - 1] - 2*y[i] + y[i + 1]) / h**2 # range
  
      for i in [N[0] + N[1] - 1]: # at 1198, or 398 = special 3
          dydt[i] = D2 * (-3*y[i] - 4*y[i - 1] + y[i - 2]) / h**2 # range
  
      for i in [N[0] + N[1]]: # 1199, or 399 = unknown
          dydt[i] = ((D1*(-3*y[i] + 4*y[i + 1] - y[i + 2])) - (D2*(-3*y[i] - 4*y[i - 1] + y[i - 2])))
  
      for i in [N[0] + N[1] + 1]: # at 1200, or 1 = special 4
          dydt[i] =  D1 * (-3*y[i + 1] + 4*y[i + 2] - y[i + 3] / h**2)  # pluss
  
      for i in range (N[0] + N[1] + 2, N[0] + N[1] + N[2] - 1): # 1202 to 1999
          dydt[i] = D1 * (y[i - 1] - 2*y[i]+ y[i + 1]) / h**2 # range
  
      return dydt
  </code></pre>