title: How to show Cartesian system in polar plot in python?
body: <p>Here I tried to add the polar plot on top of the Cartesian grid,but what I got instead was 2 separate figures(one polar another Cartesian),I want this  polar figure to be embedded in the Cartesian plot. Also I have used some of the code previously available as I am new to matplotlib.</p>
  
  <pre><code>from pylab import *
  import matplotlib.pyplot as plt
  x = [0,10,-3,-10]
  y = [0,10,1,-10]
  color=['w','w','w','w']
  
  fig = plt.figure()
  ax1 = fig.add_subplot(111)
  
  scatter(x,y, s=100 ,marker='.', c=color,edgecolor='w')
  
  circle1=plt.Circle((0,0),5,color='r',fill=False)
  circle_min=plt.Circle((0,0),4.5,color='g',fill=False)
  circle_max=plt.Circle((0,0),5.445,color='b',fill=False)
  fig = plt.gcf()
  
  
  fig.gca().add_artist(circle1)
  fig.gca().add_artist(circle_min)
  fig.gca().add_artist(circle_max)
  
  left,right = ax1.get_xlim()
  low,high = ax1.get_ylim()
  arrow( left, 0, right -left, 0, length_includes_head = True, head_width = 0.15 )
  arrow( 0, low, 0, high-low, length_includes_head = True, head_width = 0.15 )
  
  
  grid()
  
  fig = plt.figure()
  ax2 = fig.add_subplot(111)
  
  scatter(x,y, s=100 ,marker='.', c=color,edgecolor='w')
  
  circle2=plt.Circle((0,0),5,color='r',fill=False)
  circle_min=plt.Circle((0,0),4.5,color='g',fill=False)
  circle_max=plt.Circle((0,0),5.445,color='b',fill=False)
  fig = plt.gcf()
  
  
  fig.gca().add_artist(circle2)
  fig.gca().add_artist(circle_min)
  fig.gca().add_artist(circle_max)
  
  left,right = ax2.get_xlim()
  low,high = ax2.get_ylim()
  arrow( left, 0, right -left, 0, length_includes_head = True, head_width = 0.15 )
  arrow( 0, low, 0, high-low, length_includes_head = True, head_width = 0.15 )
  
  import numpy as np
  import matplotlib.pyplot as plt
  
  
  theta = np.linspace(-np.pi, np.pi, 100)  
  r1 = 1 - np.sin(3*theta)
  r2 = 1 + np.cos(theta)
  
  
  ax = plt.subplot(111, polar=True,      # add subplot in polar coordinates 
                   axisbg='Azure')       # background colour
  
  ax.set_rmax(2.2)                       # r maximum value
  ax.grid(True)                          # add the grid
  
  ax.plot(theta, r1,
          color='Tomato',                # line colour
          ls='--',                       # line style
          lw=3,                          # line width
          label='a 3-fold curve')        # label
  
  ax.plot(theta, r2, 
          color='purple',
          linewidth=3,
          ls = '-',
          label = 'a cardioid')
  
  
  ax.legend(loc="lower right")           # legend location
  
  titlefont = {
          'family' : 'serif',
          'color'  : 'black',
          'weight' : 'bold',
          'size'   : 16,
          }
  
  ax.set_title("A plot in polar coordinates", # title
               va='bottom',                   # some space below the title
               fontdict = titlefont           # set the font properties
               )
  
  
  
  grid()
  
  show()
  
  
  
  #I am getting a separate Cartesian image + a polar image while what I need   is both the things in a single image
  </code></pre>