code: protected DoubleMatrix2D createFullDataMatrix(DoubleMatrix2D SubDiagonalSymmMatrix){
  		int c = SubDiagonalSymmMatrix.columns();
  		DoubleMatrix2D ret = F2.make(c, c);
  		for(int i=0; i<c; i++){
  			for(int j=0; j<=i; j++){
  				ret.setQuick(i, j, SubDiagonalSymmMatrix.getQuick(i, j));
  				ret.setQuick(j, i, SubDiagonalSymmMatrix.getQuick(i, j));
  			}
  		}
  		return ret;
  	}
docs: Create a full data matrix starting form a symmetric matrix filled only in its subdiagonal elements.