Problem Using User Input with Function Handle

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Carl
Carl 2012-9-15
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.

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采纳的回答

Matt Fig
Matt Fig 2012-9-15
编辑：Matt Fig 2012-9-15
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

更多回答（1 个）

Wayne King
Wayne King 2012-9-15
编辑：Wayne King 2012-9-15
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);

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