Converts a linear progress value (0-1) into the corresponding eased value. In other words, if the tween is halfway done (progress of 0.5), you'd get the corresponding ease ratio like this:
//create a CustomEase with an ID of "hop"
var ease = CustomEase.create("hop", "M0,0 C0,0 0.056,0.445 0.175,0.445 0.294,0.445 0.332,0 0.332,0 0.332,0 0.414,1 0.671,1 0.991,1 1,0 1,0");
//get the eased ratio at the progress of 0.5 (halfway done):
var value = ease.getRatio(0.5);
See CustomEase for more details.