Defining symbolic derivative inside a nested function and passing the handle to command window or script

Hi All, I am a debutant in MATLAB. I am trying to define a symbolic derivative inside a nested function and then pass its handle to command window by calling the parent function. However, when I evaluate the nested function at a certain value from the command window, I get an error as shown further below.

function [f,f_d] = setFunctions_trial
f = @func;
    function y = func(x)
        y = x^2;
    end
f_d = @func_deriv;
    function y = func_deriv(x)
        syms g(s)
        g(s) = f(s);
        df = diff(g,s);
        y = df(x);
    end
end

>> clear all
>> [f,f_d] = setFunctions_trial;
>> f(2)
ans =
     4
>> f_d(2)
Error using assignin
Attempt to add "s" to a static workspace.
 See Variables in Nested and Anonymous Functions.
Error in syms (line 312)
    assignin('caller', y, ysym);
Error in setFunctions_trial/func_deriv (line 9)
        syms g(s)

For my purpose I only need symbolic derivative of the func(x) being available in command window or in another script. It need not be inside a nested function. Any other suggestions are welcome.

Thankyou,

Sid

Answer 1

[Siddhartha Harsha Ommi]

Got the answer here. What is the cause of this weird phenomenon with symbolic variables and nested function?

The following code works neatly.

function [f,f_d] = setFunctions_trial
f = @func;
    function y = func(x)
        y = x^2;
    end
f_d = @func_deriv;
    function y = func_deriv(x)
        s = sym('s');
        g = symfun(f(s),s);
        df = diff(g,s);
        y = df(x);
    end
end

>> clear all
>> [f,f_d] = setFunctions_trial;
>> f_d(2)
 
ans =
 
4

Sid