source: tags/release-1.2.2/src/Utils/medianBaseline.cc

// -----------------------------------------------------------------------
// medianBaseline.cc: Obtaining spectral baselines using a median filter.
// -----------------------------------------------------------------------
// Copyright (C) 2006, Matthew Whiting, ATNF
//
// This program is free software; you can redistribute it and/or modify it
// under the terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2 of the License, or (at your
// option) any later version.
//
// Duchamp is distributed in the hope that it will be useful, but WITHOUT
// ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
// FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
// for more details.
//
// You should have received a copy of the GNU General Public License
// along with Duchamp; if not, write to the Free Software Foundation,
// Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA
//
// Correspondence concerning Duchamp may be directed to:
//    Internet email: Matthew.Whiting [at] atnf.csiro.au
//    Postal address: Dr. Matthew Whiting
//                    Australia Telescope National Facility, CSIRO
//                    PO Box 76
//                    Epping NSW 1710
//                    AUSTRALIA
// -----------------------------------------------------------------------
#include <iostream>
#include <map>

float medVal(std::map<float,int> &themap)
{
  std::map<float,int>::iterator it;
  it = themap.begin();
  if(themap.size()%2==0) {
    for(size_t i=0;i<themap.size()/2-1;i++) it++;
    float v1 = it->first;
    it++;
    float v2 = it->first;
    return (v1+v2)/2.;
  }
  else{
    for(size_t i=0;i<themap.size()/2;i++) it++;
    return it->first;
  }
}

float *medianBaseline(float *inputArray, int dim, unsigned int boxWidth)
{

  if(boxWidth%2==0) std::cerr << "medianBaseline: boxWidth needs to be odd. Changing from " << boxWidth << " to " << boxWidth+1 <<"\n";
  boxWidth++;

  int halfWidth = boxWidth/2;

  if(halfWidth > dim) {
    std::cerr << "Box half-width bigger than array dimension. Returning input array unchanged.\n";
    return inputArray;
  }

  std::map<float,int> pixMap;
  
  float *medianArray = new float[dim];

  // Initialise the map for the first point in the array
  int curpos = 0;
  for(int i=0; i<=halfWidth; i++) {
    pixMap.insert(std::pair<float,int>(inputArray[i],i));
    //    std::cerr << "Inserting " << i << " " << inputArray[i] << "\n";
  }
  medianArray[curpos] = medVal(pixMap);

  // Do it for the rest of the points
  curpos++;
  for(;curpos<dim;curpos++){
    
    int newpix = curpos+halfWidth;
    if(newpix<dim) pixMap.insert(std::pair<float,int>(inputArray[newpix],newpix));
    //    std::cerr << "Inserting " << newpix << " " << inputArray[newpix] << "\n";

    int oldpix = curpos-halfWidth-1;
    //    if(oldpix>=0) pixMap.erase(oldpix);
    if(oldpix>=0) pixMap.erase(inputArray[oldpix]);

    medianArray[curpos] = medVal(pixMap);

  }

  return medianArray;
}