Help please with inline function

hi everyone

i am trying to run this code in matlab

clear all
clc

syms x;

fun=input('f(x):'); %enter any function you want to derive
f=inline(fun); %inline the function

z=diff(f(x)); % derive the function of x
f1=inline(z); %inline again

x0=input('Enter the iniial value of interval:');
x=x0; % store in x

for i=0:1000
    y=x;    %stores x value in y
    x=y-[f(x)/f1(x)];
    if x==y % compares the new value with the old value
        break
    end 
end
fprintf( 'The total number of iterations are:');
i
x

but this is the error I am getting please help me

f(x):(x^2)+4
??? Error using ==> inline.inline at 47
Input must be a string.

Error in ==> Newton at 7
f=inline(fun); %inline the function

[Jan]

Currently your code is not readable. Please read this: http://www.mathworks.com/matlabcentral/answers/13205-tutorial-how-to-format-your-question-with-markup

Answer 1

[Walter Roberson]

f = inline( char(fun) ); %inline the function

z = diff(f(x)); % derive the function of x
f1 = inline( char(z) ); %inline again

Answer 2

[Star Strider]

If you have R2012a or later, use symfun instead of inline, or even an anonymous function. See the documentation for symfun for details.

To use symfun,, your inplut and function declaration would then be:

syms x
fun=input('f(x):'); %enter any function you want to derive
f = symfun(sym(fun), x)

and for the response of the input:

f(x):x^2 + 2*x + 1

the symfun result is:

f(x) =   
x^2 + 2*x + 1

and you have a useful symbolic function!

What version of MATLAB are you using?