symbolic function as input to a matlab function

Hello everyone.

Let's suppose I have a symbolic function like this :

syms f(x)
f(x) = exp(x + 5);

I have to pass this symbolic function as an argument to a matlab function. Is this syntax correct?

function number = example(f)
    arguments (Input)
        f (1,1) sym
    end
    number = double(solve(f(x) == 5));

when i call the function, what is the correct syntax?

    number = example(f)

or

    number = example(f(x))

Also, the body of the function is wrong and it works only if i add "syms x" to it. Is this syntax correct or should I do it another way?

function number = example(f)
    arguments (Input)
        f (1,1) sym
    end
    sym x
    number = double(solve(f(x) == 5));

Answer 1

[Nandini]

The syntax you provided for passing a symbolic function as an argument to a MATLAB function is almost correct. However, there are a few modifications needed to make it work correctly.

First, when defining the symbolic function `f(x)`, you need to use the `sym` function to declare `x` as a symbolic variable. Here's the corrected code for defining the symbolic function:

syms f(x)
syms x
f(x) = exp(x + 5);

Next, when calling the `example` function, you need to pass the symbolic function `f` without explicitly specifying the variable `x`. The correct syntax would be:

number = example(f);

Now, let's correct the body of the `example` function. You can declare `x` as a symbolic variable within the function, and then use it in the `solve` function. Here's the corrected code:

function number = example(f)
    arguments (Input)
        f (1,1) sym
    end
    sym x
    number = double(solve(f(x) == 5, x));
end

With this corrected code, you can call the `example` function as `number = example(f);`, and it will correctly solve the equation `f(x) == 5` using the symbolic function `f` and return the solution as a double value in the variable `number`.

Hope it helps you.

[Francesco Pio]

thanks a lot, it really helps!

[VBBV]

Hi @Francesco Pio. another way to call the function is by using two input arguments to the function example as shown below.

syms f(x) x   % define x as symbolic variable
f(x) = exp(x + 5);
number = example(f,x) % pass it as input argument to the function 

number = -3.3906

function number = example(f,x)     
    number = double(solve(f(x) == 5));
end