#
#  Copyright (C) 2002  greg Landrum and Rational Discovery LLC
#  All Rights Reserved 
#
import numpy


def _CenterTForm(dataSet):
  """ INTERNAL USE ONLY

  """
  pass

def _NormalizeTForm(dataSet):
  """ INTERNAL USE ONLY

  """
  pass

def _StandardTForm(dataSet):
  """ INTERNAL USE ONLY

  """
  pass

_availTransforms = [
  ('Center',_CenterTForm,'translates so that mean(x)=0'),
  ('Normalize',_NormalizeTForm,'scales so that dot(x,x)=1'),
  ('Standardize',_StandardTForm,'scales so that dev(x)=0'),
  
  ]

def GetAvailTransforms():
  """ returns the list of available data transformations

   **Returns**

     a list of 3-tuples

       1) name of the transform (text)

       2) function describing the transform (should take an
          _MLDataSet_ as an argument)

       3) description of the transform (text)

  """
  global _availTransforms
  return _availTransforms

