InfoBitRanker.h

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// $Id$
//
//  Copyright (C) 2003-2007 Greg Landrum and Rational Discovery LLC
//   @@ All Rights Reserved @@
//  This file is part of the RDKit.
//  The contents are covered by the terms of the BSD license
//  which is included in the file license.txt, found at the root
//  of the RDKit source tree.
//
 
#include <RDGeneral/export.h>
#ifndef _RD_INFORANKER_H_
#define _RD_INFORANKER_H_
 
#include <RDGeneral/types.h>
#include <DataStructs/BitVects.h>
#include <iostream>
 
/*! \brief Class used to rank bits based on a specified measure of information
 *
 * Basically a primitive mimic of the CombiChem "signal" functionality
 * To use:
 *  - create an instance of this class
 *  - loop over the fingerprints in the dataset by calling accumulateVotes
 *method
 *  - call getTopN to get the top n ranked bits
 *
 * Sample usage and results from the python wrapper:
 * Here's a small set of vectors:
 * >>> for i,bv in enumerate(bvs): print bv.ToBitString(),acts[i]
 * ...
 * 0001 0
 * 0101 0
 * 0010 1
 * 1110 1
 *
 * Default ranker, using infogain:
 * >>> ranker = InfoBitRanker(4,2)
 * >>> for i,bv in enumerate(bvs): ranker.AccumulateVotes(bv,acts[i])
 * ...
 * >>> for bit,gain,n0,n1 in ranker.GetTopN(3): print
 *int(bit),'%.3f'%gain,int(n0),int(n1)
 * ...
 * 3 1.000 2 0
 * 2 1.000 0 2
 * 0 0.311 0 1
 *
 * Using the biased infogain:
 * >>> ranker = InfoBitRanker(4,2,InfoTheory.InfoType.BIASENTROPY)
 * >>> ranker.SetBiasList((1,))
 * >>> for i,bv in enumerate(bvs): ranker.AccumulateVotes(bv,acts[i])
 * ...
 * >>> for bit,gain,n0,n1 in ranker.GetTopN(3): print
 *int(bit),'%.3f'%gain,int(n0),int(n1)
 * ...
 * 2 1.000 0 2
 * 0 0.311 0 1
 * 1 0.000 1 1
 *
 * A chi squared ranker is also available:
 * >>> ranker = InfoBitRanker(4,2,InfoTheory.InfoType.CHISQUARE)
 * >>> for i,bv in enumerate(bvs): ranker.AccumulateVotes(bv,acts[i])
 * ...
 * >>> for bit,gain,n0,n1 in ranker.GetTopN(3): print
 *int(bit),'%.3f'%gain,int(n0),int(n1)
 * ...
 * 3 4.000 2 0
 * 2 4.000 0 2
 * 0 1.333 0 1
 *
 * As is a biased chi squared:
 * >>> ranker = InfoBitRanker(4,2,InfoTheory.InfoType.BIASCHISQUARE)
 * >>> ranker.SetBiasList((1,))
 * >>> for i,bv in enumerate(bvs): ranker.AccumulateVotes(bv,acts[i])
 * ...
 * >>> for bit,gain,n0,n1 in ranker.GetTopN(3): print
 *int(bit),'%.3f'%gain,int(n0),int(n1)
 * ...
 * 2 4.000 0 2
 * 0 1.333 0 1
 * 1 0.000 1 1
 */
namespace RDInfoTheory {
typedef std::vector<RDKit::USHORT> USHORT_VECT;
typedef std::vector<USHORT_VECT> VECT_USHORT_VECT;
 
class RDKIT_INFOTHEORY_EXPORT InfoBitRanker {
 public:
  /*! \brief the type of measure for information
   *
   */
  typedef enum {
    ENTROPY = 1,
    BIASENTROPY = 2,
    CHISQUARE = 3,
    BIASCHISQUARE = 4
  } InfoType;
 
  /*! \brief Constructor
   *
   * ARGUMENTS:
   *
   *   - nBits: the dimension of the bit vectors or the fingerprint length
   *   - nClasses: the number of classes used in the classification problem
   *(e.g. active,
   *              moderately active, inactive etc.). It is assumed that the
   *classes are
   *              numbered from 0 to (nClasses - 1)
   *   - infoType: the type of information metric
   */
  InfoBitRanker(unsigned int nBits, unsigned int nClasses,
                InfoType infoType = InfoBitRanker::ENTROPY)
      : d_dims(nBits), d_classes(nClasses), d_type(infoType) {
    d_counts.resize(0);
    for (unsigned int i = 0; i < nClasses; i++) {
      USHORT_VECT cCount;
      cCount.resize(d_dims, 0);
      d_counts.push_back(cCount);
    }
    d_clsCount.resize(d_classes, 0);
    d_nInst = 0;
    d_top = 0;
    dp_topBits = nullptr;
    d_biasList.resize(0);
    dp_maskBits = nullptr;
  }
 
  ~InfoBitRanker() {
    if (dp_topBits) {
      delete[] dp_topBits;
    }
    if (dp_maskBits) {
      delete dp_maskBits;
    }
  }
 
  /*! \brief Accumulate the votes for all the bits turned on in a bit vector
   *
   *  ARGUMENTS:
   *
   *   - bv : bit vector that supports [] operator
   *   - label : the class label for the bit vector. It is assumed that 0 <=
   *class < nClasses
   */
  void accumulateVotes(const ExplicitBitVect &bv, unsigned int label);
  void accumulateVotes(const SparseBitVect &bv, unsigned int label);
 
  /*! \brief Returns the top n bits ranked by the information metric
   *
   * This is actually the function where most of the work of ranking is
   *happening
   *
   *  \param num the number of top ranked bits that are required
   *
   *  \return a pointer to an information array. The client should *not*
   *          delete this
   */
  double *getTopN(unsigned int num);
 
  /*! \brief return the number of labelled instances(examples) or fingerprints
   *seen so far
   *
   */
  unsigned int getNumInstances() const { return d_nInst; }
 
  /*! \brief return the number of classes
   *
   */
  unsigned int getNumClasses() const { return d_classes; }
 
  /*! \brief Set the classes to which the entropy calculation should be biased
   *
   * This list contains a set of class ids used when in the BIASENTROPY mode of
   *ranking bits.
   * In this mode, a bit must be correllated higher with one of the biased
   *classes than all the
   * other classes. For example, in a two class problem with actives and
   *inactives, the fraction of
   * actives that hit the bit has to be greater than the fraction of inactives
   *that hit the bit
   *
   * ARGUMENTS:
   *   classList - list of class ids that we want a bias towards
   */
  void setBiasList(RDKit::INT_VECT &classList);
 
  /*! \brief Set the bits to be used as a mask
   *
   * If this function is called, only the bits which are present in the
   *   maskBits list will be used.
   *
   * ARGUMENTS:
   *   maskBits - the bits to be considered
   */
  void setMaskBits(RDKit::INT_VECT &maskBits);
 
  /*! \brief Write the top N bits to a stream
   *
   */
  void writeTopBitsToStream(std::ostream *outStream) const;
 
  /*! \brief Write the top bits to a file
   *
   */
  void writeTopBitsToFile(const std::string &fileName) const;
 
 private:
  /*! \brief check if we want to compute the info content for a bit based on the
   *bias list
   *
   * This what happens here:
   *    - the fraction of items in each class that hit a particular bit are
   *computed
   *    - the maximum of these fractions for classes that are not in the
   *biasList are computed
   *    - If this maximum is less than the fraction for at least one of the
   *      classes in the biaslist, the bit is considered good
   * ARGUMENTS:
   *   - resMat : the result matrix, one dimensional matrix of dimension (2*(num
   *of classes))
   *              a 2D structure is assumed with the first row containing number
   *of items of each class
   *              with the bit set and the second row to entires of each class
   *with the bit turned off
   */
  bool BiasCheckBit(RDKit::USHORT *resMat) const;
 
  /*! \brief Compute the biased info entropy gain based on the bias list
   *
   *  This what happens here:
   *    - we call BiasCheckBit to see if the bit qualifies to compute the
   *infocontent
   *    - If this bit is ok then we call InfoEntropyGain otherwise we return 0.0
   *
   * ARGUMENTS:
   *   - resMat : the result matrix, one dimensional matrix of dimension (2*(num
   *of classes))
   *              a 2D structure is assumed with the first row containing number
   *of items of each class
   *              with the bit set and the second row to entires of each class
   *with the bit turned off
   */
  double BiasInfoEntropyGain(RDKit::USHORT *resMat) const;
 
  /*! \brief Compute the biased chi qsure value based on the bias list
   *
   *  This what happens here:
   *    - we call BiasCheckBit to see if the bit qualifies to compute the
   *infocontent
   *    - If this bit is ok then we call InfoEntropyGain otherwise we return 0.0
   *
   * ARGUMENTS:
   *   - resMat : the result matrix, one dimensional matrix of dimension (2*(num
   *of classes))
   *              a 2D structure is assumed with the first row containing number
   *of items of each class
   *              with the bit set and the second row to entires of each class
   *with the bit turned off
   */
  double BiasChiSquareGain(RDKit::USHORT *resMat) const;
 
  unsigned int d_dims;     // the number of bits in the fingerprints
  unsigned int d_classes;  // the number of classes (active, inactive,
                           // moderately active etc.)
  InfoType d_type;  // the type of information measure - currently we support
                    // only entropy
  VECT_USHORT_VECT d_counts;  // place holder of counting the number of hits for
                              // each bit for each class
  USHORT_VECT d_clsCount;  // counter for the number of instances of each class
  double *dp_topBits;  // storage for the top ranked bits and the corresponding
                       // statistics
  unsigned int d_top;  // the number of bits that have been ranked
  unsigned int d_nInst;  // total number of instances or fingerprints used
                         // accumulate votes
  RDKit::INT_VECT
      d_biasList;  // if we want a bias towards certain classes in ranking bits
  ExplicitBitVect *dp_maskBits;  // allows only certain bits to be considered
};
}  // namespace RDInfoTheory
#endif