title: Calculate signature speed/velocity having timestamp and position
body: <p>I'm writing a signature software (you sign through a tablet and it processes you signature).
  I have for each point pressed by the pen its position (.getx() and .gety()) and its timestamp (.getTime()).  How can i calculate an appropriate "signing speed"? Witch kind of formula should I use? 
  It is enough to do distance/time (amount of lines written between the points/ time to write them)? Or should I find the vectorial average speed?</p>
  
  <p>Thanks to all who wants to help</p>