title: Label for circles in matplotlib
body: <p>i have constructed a very simplified code for effective stresses in the mohr circle. This is my code:</p>
  
  <pre><code>from mpl_toolkits.mplot3d import *     # für Druckplots benötigt
  from matplotlib import cm
  from math import *                     # für pi und exp benötigt
  from scipy.special import *            # für expn benötigt
  import matplotlib.pyplot as plt        # für Plotting in 2D/3D benötigt
  import numpy as np                     # für für Arrays benötigt
  import matplotlib.lines as mlines
  import os
  clear = lambda: os.system('cls')
  clear()
  #==============================================================================
  #                               Mohr Cirlce
  #==============================================================================
  
  #depth = 3000.0                  # Reservoirtiefe
  #density = 2700.0                # Dichte des überlagernden Gesteins
  #G = 12700.0                     # shear modulus [MPa]
  #E = 26000.0                     # Young´s modulus in [MPa]
  #sv = 9.81*density*depth/1e6     # vertical stress
  #sh = 0.5*sv                     # minimum horizontal stress
  cf1 = 4.0                        # Cohesion C Fault1 [MPa] 
  muef1 = 0.5                      # coefficient of friction  [MPa]
  #f1dip = 45                      # Einfallen der Störung
  p0 = 15.0                        # initial pore pressure [MPa]
  
  # Mohr failure criterion ##
  sigman = np.zeros((80))
  tauf1 = np.zeros((80))
  for i in range(0,80):
      sigman[i] = i
      tauf1[i] = muef1*sigman[i]+cf1 # Bruchgerade
  
  ## Stresses ##
  sH = 60.0
  sh = 30.0   
  smean = float((sH+sh)/2)         # Kreismittelpunkt
  shear = float((sH-sh)/2)         # Kreisradius
  
  ## Effective Stresses ##
  sHeff = sH-p0                       # effektive Vertikalspannung
  sheff = sh-p0                       # effektive Horizontalspannung
  smeaneff = float((sHeff+sheff)/2)   # Kreismittelpunkt
  sheareff = float((sHeff-sheff)/2)   # Kreisradius
  
  ## Plotting ## 
  fig=plt.figure()
  ax=fig.add_subplot(1,1,1)
  plt.plot(sigman, tauf1, "b", linewidth=1, linestyle="-", label="Bruchgerade")
  ax.axis('scaled')
  mohr=plt.Circle((smean,0), radius=shear, color='g', fill=False, label = "Mohr")
  mohreff=plt.Circle((smeaneff,0), radius=sheareff, color='r', fill=False)
  plt.title("Mohrkreise bei ...")
  ax.set_xlabel('$\sigma$ [MPa]', fontsize=12)
  ax.set_ylabel('$\tau$ [MPa]', fontsize=12)
  plt.xticks(np.arange(0, 90, 10))
  plt.yticks(np.arange(0, 45, 5))
  plt.legend(bbox_to_anchor=(1.05, 1), loc=2, borderaxespad=0., numpoints = 1)
  ax.add_patch(mohr)
  ax.add_patch(mohreff)
  plt.show()
  </code></pre>
  
  <p>My green circle represents the initial stresses, my red one the effective stresses. I want to add labels for these two circles in my legend, is this possible? I didnt' find any solution so far.</p>
  
  <p>Cheers,
  A.</p>