title: Python plot different variables on same y axis
body: <p>I want to visualize many parameters over time. Basically, I want to plot datetime on x-axis, different parameters on y-axis.</p>
  <p>My code:</p>
  <pre><code>df = 
  index                     y1        y2         y3
  2021-03-14 08:38:22   34.660422  6.278744  443.253277
  2021-03-14 08:39:11   34.853815  6.267421  446.127032
  2021-03-14 08:40:01   34.966101  6.338569  446.868933
  2021-03-14 08:41:13   34.687784  6.339623  454.871855
  2021-03-14 10:42:56  403.837103  9.091500  847.931740
  
  # plot
  plt.plot(df.index,df['y1'],'o')
  plt.plot(df.index,df['y2'],'o')
  plt.plot(df.index,df['y3'],'o')
  plt.show()
  </code></pre>
  <p>It outputs the plot. The problem is, <code>y1</code> data dominates <code>y2</code> and we cannot clearly see the second column trend. How do I address this?</p>