public double valueAt(double[] param) {
double[] sdInv = new double[nVariables];
for (int i = 0; i < nVariables; i++) {
R.setEntry(i, i, 1.0 - param[i]);
sdInv[i] = 1.0 / Sinv.getEntry(i, i);
}
DiagonalMatrix diagSdInv = new DiagonalMatrix(sdInv);
EigenDecomposition eigen = new EigenDecomposition(R);
RealMatrix eigenVectors = eigen.getV().getSubMatrix(0, nVariables - 1, 0, nFactors - 1);
double[] ev = new double[nFactors];
for (int i = 0; i < nFactors; i++) {
ev[i] = Math.sqrt(eigen.getRealEigenvalue(i));
}
DiagonalMatrix evMatrix =
new DiagonalMatrix(
ev); // USE Apache version of Diagonal matrix when upgrade to version 3.2
RealMatrix LAMBDA = eigenVectors.multiply(evMatrix);
RealMatrix SIGMA = (LAMBDA.multiply(LAMBDA.transpose()));
double value = 0.0;
RealMatrix DIF = R.subtract(SIGMA);
for (int i = 0; i < DIF.getRowDimension(); i++) {
for (int j = 0; j < DIF.getColumnDimension(); j++) {
value = DIF.getEntry(i, j);
DIF.setEntry(i, j, Math.pow(value, 2));
}
}
RealMatrix RESID = diagSdInv.multiply(DIF).multiply(diagSdInv);
double sum = 0.0;
for (int i = 0; i < RESID.getRowDimension(); i++) {
for (int j = 0; j < RESID.getColumnDimension(); j++) {
sum += RESID.getEntry(i, j);
}
}
return sum;
}
