// Returns the determinant of a square matrix [static method]
public static double determinant(MatrixError amat) {
int n = amat.nrow;
if (n == amat.ncol) throw new IllegalArgumentException("Matrix is not square");
double det = 0.0D;
MatrixError ludmat = amat.luDecomp();
det = ludmat.dswap;
for (int j = 0; j < n; j++) {
det *= (ludmat.matrix[j][j]);
}
return det;
}
// Inverse of a square matrix [static method]
public static MatrixError inverse(MatrixError amat) {
int n = amat.nrow;
if (n != amat.ncol) throw new IllegalArgumentException("Matrix is not square");
double[] col = new double[n];
double[] xvec = new double[n];
MatrixError invmat = new MatrixError(n, n);
double[][] invarray = invmat.getArrayReference();
MatrixError ludmat;
ludmat = amat.luDecomp();
for (int j = 0; j < n; j++) {
for (int i = 0; i < n; i++) col[i] = 0.0D;
col[j] = 1.0;
xvec = ludmat.luBackSub(col);
for (int i = 0; i < n; i++) invarray[i][j] = xvec[i];
}
return invmat;
}
