ExampleMeanAndDev.cpp

simple example which calculates mean and standard deviation of values in a file read from disk

Author

MIP

/*
This file is part of the BIAS library (Basic ImageAlgorithmS).

Copyright (C) 2003-2009    (see file CONTACT for details)
  Multimediale Systeme der Informationsverarbeitung
  Institut fuer Informatik
  Christian-Albrechts-Universitaet Kiel


BIAS is free software; you can redistribute it and/or modify
it under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.

BIAS 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 Lesser General Public License for more details.

You should have received a copy of the GNU Lesser General Public License
along with BIAS; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
*/

/** @example ExampleMeanAndDev.cpp
    @ingroup g_examples
    @brief  simple example which calculates mean and standard
                      deviation of values in a file read from disk
    @author MIP */


#include <bias_config.h>
#include <math.h>
#include <Base/Debug/Debug.hh>
#include <Base/Debug/Error.hh>
#include <iostream>
#include <Base/Common/BIASpragma.hh>

using namespace BIAS;
using namespace std;


int main(int argc, char *argv[]) 
{
  if (argc<3) {
    cerr << "Not enough parameters given!" << endl;
    cout << "Usage: ExampleMeanAndDev [file name] [columns]" << endl;
    exit(0);
  }
  FILE* myfile = fopen(argv[1], "r");
  const int column = atoi(argv[2]);
  char thestring[1024];
  int nummeasurements = 0;
  float *value = new float[column];
  double valuesum=0,mean=0;
  
  while (fgets(thestring, 1020, myfile)) {
    if (sscanf(thestring, "%f %f %f",&(value[0]),&(value[1]),&(value[2])) < 
        column) continue;
    nummeasurements++;
    valuesum += value[column-1];
  }
  fclose(myfile);
  mean = valuesum / double(nummeasurements); 
 
  myfile = fopen(argv[1], "r");
  nummeasurements = 0;
  valuesum = 0;
  
  while (fgets(thestring, 1020, myfile)) {
    if (sscanf(thestring, "%f %f %f",&(value[0]),&(value[1]),&(value[2])) < 
               column) continue;
    nummeasurements++;
    valuesum += (mean-value[column-1]) * (mean-value[column-1]);
  }
  valuesum /= double(nummeasurements-1); 
  cout<<"Mean is "<< mean << " and dev is "<<sqrt(valuesum)<<" on "
      <<nummeasurements<<" measurements"<<endl;
  fclose(myfile);

  return 0;
}