How to find the input to a function given the result?

Hello

I have a function called RKS which accepts 2 values T and P and gives me a value S. In the main script it looks like this:

S=RKS(T,P);

If I have S and P and I am trying to find T how can I do it using the matlab solver. I was told that I could do it this way without having to modify the RKS function itself but I have not study how to use the solver in matlab and can't figure it out. I keep getting errors. Also if there is any other way of getting T I am open to subjection.

Thanks You.

Answer 1

[Star Strider]

Here is one possibility:

RKS = @(T,P) P.^-T;
P = 5;
S = RKS(3,P);

T = fzero(@(T) RKS(T,P)-S, 1);

[Alejandro Morales]

What is the 3 in

S = RKS(3,P);

suppose to be? A random guess?.

[Star Strider]

Yes.

Both the ‘3’ and the ‘RKS’ function are random guesses. The point is to illustrate an approach to recovering ‘T’.

This assumes that the function S(P,T) is one-to-one. If the function is a power of ‘T’, periodic in ‘T’, or something else, the solution would not necessarily be unique.