how to get the final shape of a function after you got the variables?

I have this function: f1=[-3*X(1)+X(2)+X(2).^3; -X(2)-X(3)]; I if X(1)=4;X(2)=3...

i want to evaluate f1 at these value, how to do this?

Answer 1

[Thorsten]

 X = [1 2 3]; % sample values X(1) = 1, X(2) = 2, X(3) = 3;
 % evaluate function for these values
 f1= [-3*X(1)+X(2)+X(2).^3; -X(2)-X(3)];

[Ahmed]

I have to write the equations f1= [-3*X(1)+X(2)+X(2).^3; -X(2)-X(3)]; at the beginning and do some calculations and the evaluate the function

I do not want to re-write it.

[Thorsten]

Define a function

f1= @(X) [-3*X(1)+X(2)+X(2).^3; -X(2)-X(3)];

And evaluate

X = [1 2 3];
f1(X)

[Ahmed]

X(1) ... is symbolic and it does not run well,