title: how to get a d3.js graph's value at a particular point?
body: <p>I've got a group of graphs (using angular 7 and d3.js v5).
  with axis x=> date , y values, it's a curve (basis).
  I'd like to be able to enter a date and display at this particular date the value. My problem is , i do not see how to retreive the calculated values for a given date.
  Is it possible? 
  I did not find anything.</p>
  
  <p>I add an image to clarify.
  <a href="https://i.stack.imgur.com/RmUMN.jpg" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/RmUMN.jpg" alt="enter image description here"></a></p>
  
  <p>thanks for any help :)</p>