How to input equations in MATLAB and operate it?

I'm using MATLAB R2013a. I want to input an equation in Matlab like f(x) = x^2 - 2*x + 3. And I want it to be inputted by the user. I use inline() function for this. eg.

func = input('Enter a function: ','s');
f = inline(func);

And I have able to do some works with it. But I want to differentiate this equation. I was trying to use diff() function for this. But it doesn't work. When I use diff(f,x); it shows error. How can I solve my problem?

Answer 1

[Walter Roberson]

You should not use inline(). inline() has been recommended against since MATLAB 5.1, over a decade ago. inline() was replaced with anonymous functions, which can be built using str2func()

You cannot differentiate inline functions or anonymous functions. You can parse the string, and develop a set of routines to differentiate whatever set of input functions you allow. Or you can use the Symbolic Toolbox. For example,

f = sym('x^2 - 2*x + 3')
diff(f,x)

[Raihan Khalil]

this is not user input i think. This equation is given in the code. I need the user to input the equation.

[Walter Roberson]

func = input('Enter a function: ','s');
f = sym(func);
diff(f,x)

[Raihan Khalil]

Thank u.

Answer 2

[Jonathan Moussa NDAO]

You can try using the matlab builtin func str2func that convert your input in a matlab function handler like syntax('')

func = str2func(input("Enter the function, e.g @(x)2*x - 3: ", "s"));

Answer 3

[robert michael]

f(x) = x3 – x – 1 input in matlab?

[Walter Roberson]

f = @(x) x.^3 - x - 1