Help with creating a Newton-Raphson algorithm function

As a part of a MATLAB course I've been asked to create a function that will solve a mathematical function by using Newton-Raphson algorithm.

So I've written the following function:

function s=newtRaph(Y,x1)
syms x
y=diff(Y,x);
Y=subs(Y,x,x1);y=subs(y,x,x1);
for i=1:4
    xx=x1-(Y/y);
    x1=xx;
end
s=x1;

And called it in the script like so:

syms x
y=x-cos(x);
newtRaph(y,3)

The problem is that i get the following ans instead of the solution:

ans =
 
(4*(cos(3) - 3))/(sin(3) + 1) + 3

Can anyone tell me what am I doing wrong?

Answer 1

[madhan ravi]

Can anyone tell me what am I doing wrong?

Since you created a function with a single output you have to also call it with an output .

as below:

Solution=newtRaph(y,3)

[IKIK]

The problem is not that it called "ans", the problem is that I need to get a single number as an answer (around 0.7)

[madhan ravi]

Try

double(Solution)

[madhan ravi]

or try this file exchange https://www.mathworks.com/matlabcentral/fileexchange/4313-newton-raphson?s_tid=answers_rc2-1_p4_MLT

[IKIK]

or try this file exchange https://www.mathworks.com/matlabcentral/fileexchange/4313-newton-raphson?s_tid=answers_rc2-1_p4_MLT

Maybe that is the solution but it is way beyond my level of understanding.

Thank you for your help

[madhan ravi]

Anytime :) ,If it helped you make sure to accept the answer

Answer 2

[Greg Heath]

Add the line

ans = ans

Hope this helps.

Thank you for formally accepting my answer

Greg

[IKIK]

Where should I add it?