How to input equations in MATLAB and operate it?

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Raihan Khalil
Raihan Khalil 2016-1-1
评论： Walter Roberson 2022-6-23
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?

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采纳的回答

Walter Roberson
Walter Roberson 2016-1-1
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)

更多回答（2 个）

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"));
robert michael
robert michael 2022-6-22
f(x) = x3 – x – 1 input in matlab?

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