title: How can I plot two different variables from the same column in Altair?
body: <p>A very newbie question but very new in using Altair library. I have Dates as X-axis and and in Y column containing 0 and 1. I want two lines one for 0 and one for 1 both of different colours. How to do it?</p>
  <p><a href="https://i.stack.imgur.com/J9oUJ.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/J9oUJ.png" alt="enter image description here" /></a></p>