title: How to detect a turning point of a graph with Python
body: <p>I have an exponential decay like graph of x and y values with a turning point marked in a diagram below. My question is, with or without the noises, how can I detect the region or the middle point of the turning point using Python? The values are in csv file given in this <a href="http://www.filedropper.com/phish1_2" rel="nofollow noreferrer">link</a>.</p>
  
  <p>UPDATES: This is more clearer diagram showing the turning/changing point. </p>
  
  <p><a href="https://i.stack.imgur.com/qBPho.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qBPho.png" alt="enter image description here"></a></p>