How can I turn an equation into a string for input?

A function I am trying to use requires the function input to be a string. For example taking the equation "f(x)=x^2 - x + 5" as an input, but needing to be a string.

I am unsure of how to turn this into a string that the function will then accept (uses feval). All the questions I've found from researching use "str2sym" but I don't believe this is doing what I need.

Thanks in advance for your help.

[Johannes Fischer]

How exactly is the function defined in your code? "f(x)=x^2 - x + 5" already looks like a string to me.

[Thomas Smith]

Well that's half my issue I think. I am not sure how to define it properly, it's a very basic thing I cannot seem to find the answer for.

What I have tried to write is the equivalent of:

f='x^2-x+5';

Then I would call the function:

function(f,a,b,c)

and I will get an error due to how I have defined f (where a,b,c are just parameters to add for the operation). The function comments has "f is the function input as a string 'f' "

Answer 1

[darova]

str2func should work:

s = input('Enter the function:\n');
% Enter the function:
% '@(a,x) a*sin(x) - 1/2'
f = str2func(s);

Dont forget quotes