How can i fix the Error at 1

I cannot run my code because it says syntax error at "1" in line 2

f=@(x)+(x^3)-(x^1);
fd=@(1)+(3(x^2))+(x^-2));
a= round (input ('Enter Your Initial Value(x) :'),1);
tol = 0.0002; % 4 decimal places
fa = round(feval (f,a),1);
fda = round(feval (fd,a),1);
al = round((a-(fa/fda)),1);
error = round(abs((al-a)/al),1);
iter =0;
disp (' n Xn F(x) F(x) Xn+1 Error') disp (' -----------------------------------------------------------')
while (error>= tol)
    iter = iter+1;
    al = round(a-(fa/fda),1);
    fal = round(feval(f,al),1);
    fdal = round((feval(fd,al)),1);
    error = round(abs(((al-a)/al)*100),1);
fprintf('%2i\t %f\t %f\t %f\t %f\t %f\t \n',iter,a,fa,fda,al,error)
if (error>=tol) a = al; fa = fal; fda = fdal;
end end

[Rik]

A classmate just posted here.

Answer 1

[Walter Roberson]

fd=@(x) (1)+(3*(x.^2))+(x.^-2));

[Amirah Sofia]

Thank you for your answer 😃

Answer 2

[Rik]

You probably mean this instead:

fd=@(x)+(3*(x^2))+(x^-2);
%    ^    ^             ^
%    |    add the *     remove the extra parenthesis
%    x instead of 1

On the other lines there are also several issues. Below is my attempt at debugging your code. It runs for a=100, although I can't tell if the output makes sense.

f=@(x) (x^3)-(x^1);
fd=@(x) (1)+(3*(x^2))+(x^-2);
a= round (input ('Enter Your Initial Value(x) :'),1);
tol = 0.0002; % 4 decimal places
fa = round(f(a),1);
fda = round(fd(a),1);
al = round((a-(fa/fda)),1);
error = round(abs((al-a)/al),1);
iter =0;
disp (' n Xn F(x) F(x) Xn+1 Error')
disp (' -----------------------------------------------------------')
while (error>= tol)
    iter = iter+1;
    al = round(a-(fa/fda),1);
    fal = round(f(al),1);
    fdal = round((fd(al)),1);
    error = round(abs(((al-a)/al)*100),1);
    fprintf('%2i\t %f\t %f\t %f\t %f\t %f\t \n',iter,a,fa,fda,al,error)
    if (error>=tol)
        a = al; fa = fal; fda = fdal;
    end
end

[Amirah Sofia]

Thank you for the answer. i can run the code but i cannot get the answer as i expected. it might be because of my interpretation of the question given to coding in MATLAB. Just informing you that this is the question given: By using MATLAB Coder, find the positive root of f(x) = 1+x^3 - 1/x using Newton-Raphson Method. Plot y=1+x^3 y=1/x in the same plane.

[Rik]

Then you probably mean

f=@(x) 1 + (x.^3) - (x.^-1);
%            ^        ^
%          these dots are to enable array operations

And if fd is intended as the derivative of f, you should do remove the 1+ term:

fd=@(x) (3*x.^2) + (x.^-2);

Your code is also uncommented, so without looking up the Newton-Raphson method I can't tell in which step you have an error. Try to write the algorithm in comments first and then write the code for each step.

[ROBBIE DEXTER UKAU]

but 1 is there because its the derivative of x what do you mean by removing the 1+?

[Rik]

@Robbie, there is no x in the original function (only a cube and reciprocal), so why would there be a 1+ in the derivative?