/*
   Standard functions 

   B. Craver
   11/16/05

*/

// Averages the entries in an array
Double_t average(Int_t total, Double_t x[])
{
  Int_t sum = 0; Int_t entry_counter = 0; Double_t avg = -1;
  //cout << "total = " <<total<<endl;
  for (entry_counter = 0; entry_counter < total; entry_counter++)
    {
      sum += x[entry_counter];
      //cout << "x[" <<entry_counter<< "] = " <<x[entry_counter]<<endl;
    }

  if (total != 0) avg = sum / (Double_t) total;

  return (avg);
}

// Returns entry with maximum value
Int_t get_max_entry(Int_t NUMBER_OF_ENTRIES, Int_t input_array[])
{
  Int_t max_entry = -1;  Int_t max_value = 0;  Int_t entry_counter = 0;

  for (entry_counter = 0; entry_counter < NUMBER_OF_ENTRIES; entry_counter++)
    {
      if (input_array[entry_counter] > max_value)
	{
	  //cout << "input_array[" <<entry_counter<< "] = " <<input_array[entry_counter]<<endl;
	  max_value = input_array[entry_counter];
	  max_entry = entry_counter;
	}
    }
  
  return (max_entry);
}


// Returns entry at which value of array reaches a threshold
// Begins scanning at maximum bin and scans toward left or right edge
Int_t get_threshold_entry(Int_t NUMBER_OF_ENTRIES, Int_t input_array[], Double_t THRESHOLD, TString edge = "left")
{
  Int_t bin_counter = 0;  Bool_t found = false;
  
  bin_counter = get_max_entry(NUMBER_OF_ENTRIES, input_array);
  while (!found && ( (bin_counter >= 0) && (bin_counter <= NUMBER_OF_ENTRIES) ) )
    {
      if (input_array[bin_counter] <= THRESHOLD)
    	{
	  found = true;
	  //cout << "threshold reached at bin: " <<bin_counter<<endl;
	  return (bin_counter);
	}
      if (edge == "left") bin_counter--;
      if (edge == "right") bin_counter++;
    }
  
  // Threshold not reached    
  return(-1);
}


// Returns the x-value corresponding to y for the passed line (x1, y1), (x2, y2).
extrapolate_x(Int_t x1, Int_t x2, Int_t y1, Int_t y2, Int_t y)
{
  Double_t slope = 0.;  Double_t y_int = 0.;
  Int_t x;
  
  if ( x2 != x1) // Non-infinite slope
    {
      if (y2 != y1) // Non-zero slope
	{
	  //cout << "x2 - x1 = " <<(x2 - x1)<<endl;
	  slope = (Double_t) (y2 - y1) / (x2 - x1);  
	  //cout << "slope = " <<slope<<endl;
	  y_int = (Double_t) y2 - (slope * x2);
	  //cout << "y_int = " <<y_int<<endl;
	  
	  x = (Int_t) ( ((Double_t) y) - y_int) / slope;
	  //cout << "x = " <<x<<endl;
	  return (x);
	}
      else { // Zero slope
	return (+1e35);
      }
    }
  else { // Infinite slope
    return (-1e35);
  }
  
}