title: Pyplot colormap line by line
body: <p>I'm beginning with plotting on python using the very nice pyplot. I aim at showing the evolution of two series of data along time. Instead of doing a casual plot of data function of time, I'd like to have a scatter plot (data1,data2) where the time component is shown as a color gradient. </p>
  
  <p>In my two column file, the time would be described by the line number. Either written as a 3rd column in the file either using the intrinsic capability of pyplot to get the line number on its own.</p>
  
  <p>Can anyone help me in doing that ?</p>
  
  <p>Thanks a lot.</p>
  
  <p>Nicolas</p>