如何通过 MathNet 在 C# 中找到函数的值

Question

I need to find the function's value for the given value. For example, the function is 3x-6, and I would like to find f(1),

using MathNet.Numerics;
using MathNet.Symbolics;
using Expr = MathNet.Symbolics.SymbolicExpression;        
        
var x = Expr.Variable("x");
var func = 3*x - 6;
// var value = func.Evaluate?

Should I use method of evaluate? How can I do this?

Answer 1

Your expression and evaluation is not correct.

You can do a method that takes x as parameter and by using the right code you get the right result.

Here is an working example with inline comments/explanation to your question. You can change your equation and do what ever with it. Enjoy:

public static double MyFunc(int x)
{
    // pass one or multiple variable in equation
    var variables = new Dictionary<string, FloatingPoint>
    {
        { "x", x }
    };

    //transfer equation from string to expression
    Expression expression = Infix.ParseOrThrow("3*x-6");
    
    //evaluate the result in double
    double result = Evaluate.Evaluate(variables, expression).RealValue;
    return result;
}

Now run it, and pass MyFunc(1) which is like f(1) , it returns -3 , pass MyFunc(2) returns 0 and pass MyFunc(3) returns 3 and so on etc.