title: Minimize function with many parameters
body: <p>I want to minimize a function in order to obtain some parameters' value of : a,e,I,Omega,om,tp.</p>
  
  <p>I use this "module" : docs.scipy.org/doc/scipy/reference/generated/scipy.optimize.minimize.html. </p>
  
  <p>My function has 13 parameters:</p>
  
  <p><img src="https://i.stack.imgur.com/P7z5C.png" alt="Function I want to reduce"></p>
  
  <p>I imported : <code>from scipy.optimize import minimize</code>. Then I try to minimize it.And  the error occurs:</p>
  
  <p><img src="https://i.stack.imgur.com/WPzXi.png" alt="Minimize code + error message"> </p>
  
  <p>Would someone help to solve this problem? </p>
  
  <p>PS: I started python one week ago that may explain this syntax of the program, however I'm willing to improve myself.</p>
  
  <pre><code>from numpy import *
  import numpy as np
  import scipy as sp
  from scipy.optimize import minimize
  import matplotlib.pyplot as plt
  from pylab import *
  from os import chdir
  chdir("/Users/benjaminjaillant/Desktop")
  
  def Chi_VLT(a,e,I,tp,Omega,om,Mbh,R0,Vr_bh,alpha_bh,V_alp_bh,delta_bh,V_del_bh):
      return sum(((Vr_etoile(t_vr_VLT*365*24*3600,a,e,I,tp,om,Mbh,Vr_bh)/1000)-vr_VLT)**2/vr_error_VLT**2) + sum(((alpha_etoile_IR(t_orbit_VLT*365*24*3600,a,e,I,tp,Omega,om,Mbh,alpha_bh,V_alp_bh,R0)*206264806.246)-Ra_VLT)**2/Ra_error_VLT**2) + sum(((delta_etoile_IR(t_orbit_VLT*365*24*3600,a,e,I,tp,Omega,om,Mbh,delta_bh,V_del_bh,R0)*206264806.246)-Dec_VLT)**2/Dec_error_VLT**2)
  
  
  x0 = [1.5e14,0.8,2.5,63.10e9,4,1,8.5e36,2.5e20,2000,1.3e-8,-10e-18,2e-9,1.5e-17]
  
  res = minimize(Chi_VLT, x0 , method='nelder-mead',options={'xtol': 1e-4,'maxiter':50 ,'disp': True})
  
  print res.message
  print res.x
  </code></pre>