public ThetaEquation(String equation, double tstart, double tend, double dt){
		this.tstart = tstart;
		this.tend = tend;
		this.dt = dt;
		
		equ = new Equation(equation);
		Vector<Variable> variables = equ.getVariables();
		if(variables.size()==0){
			theta = new Variable("t");
		}
		else{
			if(variables.size()!=1)
				throw new EquationException("Invalid Theta Equation: " + equation);
			theta = variables.firstElement();
			if(!theta.getName().equals("t"))
				throw new EquationException("Invalid Theta Equation: " + equation);
		}
	}