function - MATLAB Equation as User Input to work with -

i'm trying write simple script request equation input , calculate function more once without requesting user input.

my current script defined f function handle , executed function 2 times, i'm asking new equation, not desirable.

f = @(x) input('f(x) = '); = f(2);   % requests user input b = f(3);   % requests user input again 

and should more (not working).

func = input('f(x) = '); f = @(x) func; = f(2); b = f(3); 

and here without user input idea try achieve.

f = @(x) x^2; = f(2); b = f(3); 

i think found solution symbolic math toolbox, not have addon, cannot use/test it.

is there solution?

there's no need symbolic mathematics toolbox here. can still use input. bear in mind default method of input directly take input , assign variable input assumed syntactically correct according matlab rules. that's not want. you'll want take input string using 's' option second parameter use str2func convert string anonymous function:

func = input('f(x) = ', 's'); f = str2func(['@(x) ' func]); = f(2); b = f(3); 

take note had concatenate @(x) anonymous function string inputted function provided input.

example run

let's want create function squares every element in input:

>> func = input('f(x) = ', 's'); f(x) = x.^2 >> f = str2func(['@(x) ' func])  f =       @(x)x.^2  >> = f(2)  =       4  >> b = f(3)  b =       9 

take special note assumed function element-wise square each elements in input. . operator in front of exponentiation operator (i.e. ^) important.