title: Python - different size subplots in matplotlib
body: <p>I have 4 subplots, i achieve to plot 3 subplots on 1 line but i can t add an other plot on a second line which must have the same width of the 3 figures.
  The first 3 figures :
  <a href="https://i.stack.imgur.com/0kBUR.png" rel="noreferrer"><img src="https://i.stack.imgur.com/0kBUR.png" alt="enter image description here"></a></p>
  
  <p>The second figure, i want to add:</p>
  
  <p><a href="https://i.stack.imgur.com/CqYmQ.png" rel="noreferrer"><img src="https://i.stack.imgur.com/CqYmQ.png" alt="enter image description here"></a></p>
  
  <p>I try that :</p>
  
  <pre><code>plt.close()
  
  font={'family':'sans-serif','weight':'normal','size':'14'}
  plt.rc('font',**font)
  
  fig, axes = plt.subplots(nrows=3, ncols=1)
  
  
  plt.tight_layout(pad=0.05, w_pad=0.001, h_pad=2.0)
  ax1 = plt.subplot(231) # creates first axis
  
  #ax1.text(20, 2500, 'CYCLE :', size=14) 
  
  #ax1.text(1000, 2500, str((image)*50+50), size=14) 
  
  ax1.tick_params(labelsize=8) 
  ax1.set_xticks([0,2000,500,1000,1500])
  ax1.set_yticks([0,2000,500,1000,1500])
  ax1.tick_params(labelsize=8) 
  ax1.imshow(mouchetis[::-1,::],alpha=0.6)
  ax1.imshow(V_exp_invmaskA,cmap='hot',extent=(X.min(),2015,Y.min(),2015), alpha=0.4)
  i1 = ax1.imshow(V_maskA,cmap='hot',extent=(X.min(),2015,Y.min(),2015),alpha=0.8)
  ax1.set_xticklabels([0,2000,500,1000,1500])
  ax1.set_yticklabels([0,2000,500,1000,1500])
  ax1.set_title("MASQUE A", y=1.05, fontsize=10)
  
  
  ax2 = plt.subplot(232) # creates second axis
  ax2.set_xticks([0,2000,500,1000,1500])
  ax2.set_yticks([0,2000,500,1000,1500])
  ax2.imshow(mouchetis[::-1,::],alpha=0.6)
  ax2.imshow(V_exp_invmaskB,cmap='hot',extent=(X.min(),2015,Y.min(),2015), alpha=0.4)
  i2 = ax2.imshow(V_maskB,cmap='hot',extent=(X.min(),2015,Y.min(),2015),alpha=0.8)
  ax2.set_title("MASQUE B", y=1.05, fontsize=10)
  ax2.set_xticklabels([])
  ax2.set_yticklabels([])
  
  
  ax3 = plt.subplot(233) # creates first axis
  ax3.set_xticks([0,2000,500,1000,1500])
  ax3.set_yticks([0,2000,500,1000,1500])
  ax3.imshow(mouchetis[::-1,::],alpha=0.6)
  ax3.imshow(V_exp_invmaskC,cmap='hot',extent=(X.min(),2015,Y.min(),2015), alpha=0.4)
  i3 = ax3.imshow(V_maskC,cmap='hot',extent=(X.min(),2015,Y.min(),2015),alpha=0.8)
  ax3.set_xticklabels([])
  ax3.set_yticklabels([])
  </code></pre>
  
  <p>#Here i add the fourth figure but i dont know how i can do...</p>
  
  <pre><code>ax4 = plt.subplot(234)
  ax4.plot(cycles,res_meanA,'ko',label='A',markersize=5,markerfacecolor='None')
  
  ax4.legend(loc=2,prop={'size':12})
  ax4.subplots_adjust(left=0.15)
  plt.show()
  </code></pre>