Divergence between paper scaled sigmoid and package scaled sigmoid

[r-dion]

Hello,

Firstly, thank you for your work !

I am using your NAB metric, and exploring its implementation I found some divergences around the scaled sigmoid.

In the NAB paper (Lavin2015), the scaled sigmoid is defined as

for Atp in [0,1] and Afp in [-1,0].

In the implementation, the scaled sigmoid is defined as follows (skiping the docstrings):

def scaledSigmoid(relativePositionInWindow):
  if relativePositionInWindow > 3.0:
    # FP well behind window
    val = -1.0
  else:
    val = 2*sigmoid(-5*relativePositionInWindow) - 1.0

  return val

Is it deliberate that (Atp - Afp) is replaced by a constant (2 is this case) ? It changes some results.

Thank you for your time.