Problem Using User Input with Function Handle

I am attempting to write a very short program that will requests a simple function of x and then take the numerical approximation of the function using quadv(). I am having a simple problem with not having the variable of the function declared before it is received from the user input. I'm sure this is a simple problem that I can't see because I am simply not that good with matlab.

g = input('Request a Function of (x): ');
f = @(x) g
Q = quadv(f,0,pi)

I know this program would work if 'g' was simply defined inside the code as being something like sin(x), cos(x), and so on but I cannot figure a way to get user input to work with this short piece of code.

Any help with this would be greatly appreciated.

Answer 1

[Matt Fig]

If you are writing a function, it is probably best to dispense with input prompts and let the user pass in a function handle like most other functions. But,

>> g = vectorize(inline(input('Request a Function of (x): ','s')));
Request a Function of (x): sin(x)
>> quadl(g,0,pi/2)

ans =

      1.0000

[Carl]

Thank you so much that works perfectly.

Answer 2

[Wayne King]

One thing you can use is str2func

   g = input('Request a Function of (x): ','s');
   % assume user inputs cos
   f = str2func(g);
   Q = quad(f,0,pi);