lookup_table.cpp

#include "lookup_table.h"

LookupTable::LookupTable(double *points, int num_points)
{
  // Note: Actual array size is 2*num_points

  m_Points = points;
  m_nPoints = num_points;
}

double LookupTable::getValue(double x)
{
  // Note: Assumes points are monotonically increasing in X!

  int i=0;
  while (x>m_Points[i*2] && i<m_nPoints)
    i++;

  if (i==0)
    return m_Points[1];

  if (i>=m_nPoints)
    return m_Points[(m_nPoints-1)*2+1];

  double ratio =
    (x - m_Points[(i-1)*2])
    / (m_Points[i*2] - m_Points[(i-1)*2]);

  return m_Points[(i-1)*2+1]*(1-ratio) + m_Points[i*2+1]*(ratio);
}