CalculateLeftHandSide

void LinearElement::CalculateLeftHandSide(MatrixType& rLeftHandSideMatrix, ProcessInfo& rCurrentProcessInfo)
	       {
 	
		bool CalculateStiffnessMatrixFlag = true;
		bool CalculateResidualVectorFlag = false;
		Vector temp = Vector();
		CalculateAll(rLeftHandSideMatrix, temp, rCurrentProcessInfo, CalculateStiffnessMatrixFlag,   CalculateResidualVectorFlag);
		
		}

the other available function is

 virtual void CalculateLeftHandSide(VectorType& rLeftHandSideVector, ProcessInfo& rCurrentProcessInfo)
	{
		if(rLeftHandSideVector.size()!=0)
			rLeftHandSideVector.resize(0);
	}

As it is clear in the first one LHS is a matrix and in the second one is a vector