linearCVCoefficent(D, dataElem, groupIdx, dataElemGroupIdx, m_dap)

function cvCoef = linearCVCoefficent(D, dataElem, groupIdx, dataElemGroupIdx, m_dap)
% Linear Cross Validation Coefficent

%MacLachlan, G.J. Discriminant Analysis and Statistical Pattern
% Recognition, Wiley

n = sum(m_dap.constants.numElemPerGrp);
n_i = m_dap.constants.numElemPerGrp(groupIdx);
g = m_dap.constants.numGrp;
d_ii = (dataElem - m_dap.meanList{groupIdx}) * D * (dataElem - m_dap.meanList{groupIdx})';
if groupIdx == dataElemGroupIdx
    cvCoef = ((n - g - 1) * n_i^2 / (n_i - 1)) / ((n - g) * (n_i - 1) - n_i * d_ii);
else
    d_iu = (dataElem - m_dap.meanList{groupIdx}) * D * (dataElem - m_dap.meanList{dataElemGroupIdx})';
    d_uu = (dataElem - m_dap.meanList{dataElemGroupIdx}) * D * (dataElem - m_dap.meanList{dataElemGroupIdx})';
    cvCoef = ((n - g + 1) / (n - g)) * (1 + n_i * d_iu^2 / (d_ii * ((n - g) * (n_i - 1) - n_i * d_uu)));
end