title: Show the values in the grid using matplotlib
body: <p>I m trying to generate heatmaps for the some data and my code is shown below:</p>
  
  <pre><code>data = [['basis', 2007, 2008],
          [1, 2.2, 3.4],
          [2, 0, -2.2],
          [3, -4.1, -2.5],
          [4, -5.8, 1.2],
          [5, -5.4, -3.6],
          [6, 1.4, -5.9]]
  
  x_header = data[0][1:]
  y_header = [i for i in range(1, 13)]
  data=data[1:]
  for i in range(len(data)):
      data[i] = data[i][1:]
  arr = np.array(data)
  fig, ax = plt.subplots()
  #heatmap = plt.pcolor(arr, cmap = 'RdBu')
  norm = MidpointNormalize(midpoint=0)
  im = ax.imshow(data, norm=norm, cmap=plt.cm.seismic, interpolation='none')
  
  ax.set_xticks(np.arange(arr.shape[1]), minor=False)
  ax.set_yticks(np.arange(arr.shape[0]), minor=False)
  ax.xaxis.tick_top()
  ax.set_xticklabels(x_header, rotation=90)
  ax.set_yticklabels(y_header)
  
  fig.colorbar(im)
  plt.show()
  </code></pre>
  
  <p>It generates the image</p>
  
  <p><img src="https://i.stack.imgur.com/S4bnx.png" alt="enter image description here"></p>
  
  <p>I also want to show values inside the grid.  Is there any way to do that?</p>