title: How to arrange data structure for pcolormesh?
body: <p>I have data below with much more data points. I want to create a heatmap(potential landscape) of X,Y, Z.</p>
  <p>X and Y are the positions, whilst Z is the corresponding values of the position for coloring. They're in three arrays of equal length.</p>
  <pre><code>X = [0.2, -1.78, -3.82, -1.34]
  Y = [9.18, 9.87, 7.75, 9.38]
  Z = [6.85, 7.51, 7.32, 6.98]
  df_qp = pd.DataFrame(list(zip(X,Y,Z)), columns = ['PC1', 'PC2', 'QP'])
  </code></pre>
  <p>I mad grid like that</p>
  <pre><code>xx, yy = np.meshgrid(X, Y)
  </code></pre>
  <p>and</p>
  <pre><code>plt.pcolormesh(xx,yy,Z)
  </code></pre>
  <p>is not working and I think I have to arrange Z data to 2D array and I don't how to arrange the data. Can someone give me some advice?
  Or are there better plots for the data?</p>