how to dynamically instantiate a new NonlinearObjectiveFunction through a string with Accord.net

i am working on project that it is implementing a one of the non linear optimization algorithm and to achieve that i chose to work with c# and wpf as platform i found how to implement the algorithm and that by using the Accord.net library and that by doing so

        // Suppose we would like to minimize the following function:
        // 
        //    f(x,y) = min 100(y-x²)²+(1-x)²
        // 
        // Subject to the constraints
        // 
        //    x >= 0  (x must be positive)
        //    y >= 0  (y must be positive)
        // 

        // First, let's declare some symbolic variables
        double x = 0, y = 0; // (values do not matter)

        // Now, we create an objective function
        var f = new NonlinearObjectiveFunction(

            // This is the objective function:  f(x,y) = min 100(y-x²)²+(1-x)²
            function: () => 100 * Math.Pow(y - x * x, 2) + Math.Pow(1 - x, 2),

            // And this is the vector gradient for the same function:
            gradient: () => new[]
            {
    2 * (200 * Math.Pow(x, 3) - 200 * x * y + x - 1), // df/dx = 2(200x³-200xy+x-1)
    200 * (y - x*x)                                   // df/dy = 200(y-x²)
            }
        );

and like that i managed my way to make it work i tested it with my teacher equation and everything went good and in goal to make the project a more presentable picture i wanted to create an interface for it to be easy to be used by the end users and at that moment the problem occurs i didn't find a way to parse the given equation dynamically

even that in the library description they mentioned that :

    //
    // Summary:
    //     Creates a new objective function specified through a string.
    //
    // Parameters:
    //   numberOfVariables:
    //     The number of parameters in the function.
    //
    //   function:
    //     A lambda expression defining the objective function.
    public NonlinearObjectiveFunction(int numberOfVariables, Func<double[], double> function);

i searched in many resources to achieve that but no clue found all what i found is that i can only create the quadratic equation of the type

ax^2 + bx + c = 0 with the constructor new QuadraticObjectiveFunction("x²+y²+3z+6"); i wish that someone help me find how to achieve the same feature or at least give me a hint to how to reformulate the other non linear objective function types from humain format to C# code

greetings ...

**

Update :

** i was trying to solve the problem with the wrong way the answer is to use R.net or the matlab COM to achieve what i want