WeightedMean.cpp

#include "MantidAlgorithms/WeightedMean.h"

namespace Mantid {
namespace Algorithms {

// Algorithm must be declared
DECLARE_ALGORITHM(WeightedMean)

bool WeightedMean::checkCompatibility(
    const API::MatrixWorkspace_const_sptr lhs,
    const API::MatrixWorkspace_const_sptr rhs) const {
  if (lhs->YUnit() != rhs->YUnit()) {
    g_log.error("The two workspaces are not compatible because they have "
                "different units for the data (Y).");
    return false;
  }
  if (lhs->isDistribution() != rhs->isDistribution()) {
    g_log.error("The two workspaces are not compatible because one is flagged "
                "as a distribution.");
    return false;
  }

  return BinaryOperation::checkCompatibility(lhs, rhs);
}

/** Performs a simple check to see if the sizes of two workspaces are
 * identically sized
 *  @param lhs :: the first workspace to compare
 *  @param rhs :: the second workspace to compare
 *  @retval "" The two workspaces are size compatible
 *  @retval "<reason why not compatible>" The two workspaces are NOT size
 * compatible
 */
std::string WeightedMean::checkSizeCompatibility(
    const API::MatrixWorkspace_const_sptr lhs,
    const API::MatrixWorkspace_const_sptr rhs) const {
  // in order to be size compatible then the workspaces must be identically
  // sized
  if (lhs->size() == rhs->size()) {
    return "";
  } else {
    return "Workspaces not identically sized.";
  }
}

void WeightedMean::performBinaryOperation(const MantidVec &lhsX,
                                          const MantidVec &lhsY,
                                          const MantidVec &lhsE,
                                          const MantidVec &rhsY,
                                          const MantidVec &rhsE,
                                          MantidVec &YOut, MantidVec &EOut) {
  (void)lhsX; // Avoid compiler warning
  const size_t bins = lhsY.size();
  for (size_t j = 0; j < bins; ++j) {
    if (lhsE[j] > 0.0 && rhsE[j] > 0.0) {
      const double err1 = lhsE[j] * lhsE[j];
      const double err2 = rhsE[j] * rhsE[j];
      YOut[j] = (lhsY[j] / err1) + (rhsY[j] / err2);
      EOut[j] = (err1 * err2) / (err1 + err2);
      YOut[j] *= EOut[j];
      EOut[j] = sqrt(EOut[j]);
    } else if (lhsE[j] > 0.0 && rhsE[j] <= 0.0) {
      YOut[j] = lhsY[j];
      EOut[j] = lhsE[j];
    } else if (lhsE[j] <= 0.0 && rhsE[j] > 0.0) {
      YOut[j] = rhsY[j];
      EOut[j] = rhsE[j];
    } else {
      YOut[j] = 0.0;
      EOut[j] = 0.0;
    }
  }
}

void WeightedMean::performBinaryOperation(const MantidVec &lhsX,
                                          const MantidVec &lhsY,
                                          const MantidVec &lhsE,
                                          const double rhsY, const double rhsE,
                                          MantidVec &YOut, MantidVec &EOut) {
  UNUSED_ARG(lhsX);
  assert(lhsX.size() == 1);
  // If we get here we've got two single column workspaces so it's easy.
  if (lhsE[0] > 0.0 && rhsE > 0.0) {
    const double err1 = lhsE[0] * lhsE[0];
    const double err2 = rhsE * rhsE;
    YOut[0] = (lhsY[0] / err1) + (rhsY / err2);
    EOut[0] = (err1 * err2) / (err1 + err2);
    YOut[0] *= EOut[0];
    EOut[0] = sqrt(EOut[0]);
  } else if (lhsE[0] > 0.0 && rhsE <= 0.0) {
    YOut[0] = lhsY[0];
    EOut[0] = lhsE[0];
  } else if (lhsE[0] <= 0.0 && rhsE > 0.0) {
    YOut[0] = rhsY;
    EOut[0] = rhsE;
  } else {
    YOut[0] = 0.0;
    EOut[0] = 0.0;
  }
}

} // namespace Algorithms
} // namespace Mantid