contrastfit2saturationindex

  CONTRASTFIT2SATURATIONINDEX - Compute Saturation Index 

    SI = CONTRASTFIT2SATURATIONINDEX(CONTRAST, RESPONSE)

   Given contrast in 1 percent steps in CONTRAST, this function
   computes the "saturation index" that is defined as:

   SI = (Rmax - R(100)) / (Rmax - R(0))

   This is the amount of "super saturation" at 100% contrast.

   Units of contrast can be percent or from 0 to 1.

   If Rmax == R(0), then the measure is undefined and the index that is
   returned is NaN.

   This index is called MI in Peirce 2007 (JoV)