what is the wrong in this?

Error using mupadmex
Error in MuPAD command: Index exceeds matrix dimensions.

Error in sym/subsref (line 1577)
        B = mupadmex('symobj::subsref',A.s,inds{:});

Error in NewtonMethod (line 13)
 x(n+1)=(x(n)-(f(x))/int(f(x)));

Answer 1

[Walter Roberson]

We would need to see the code to be sure, but probably f(x) is a symbolic expression that involves indexing a variable at a position that does not exist.

[Wesam Hassan]

it is the code

clc

syms x

f(x)= input('f(x)=');
a = input('a=');
b = input('b=');
n=2;
x(1)=a;
x(n)=(x(n-1)-(f(x)/int(f(x))));
while x(n-1)~= x(n)
    x=x(n);
 x(n+1)=(x(n)-(f(x))/int(f(x)));
    n=n+1;
end
display(x(n))
n=2;
x(1)=b;

x(n)=(x(n-1)-(f(x)/int(f(x))));
while x(n-1)~= x(n)
    x=x(n);
 x(n+1)=(x(n)-(f(x))/int(f(x)));
    n=n+1;
end
display(x(n))
n=2;
x(1)=(a+b)/2;
x(n)=(x(n-1)-(f(x)/int(f(x))));
while x(n-1)~= x(n)
    x=x(n);
 x(n+1)=(x(n)-(f(x))/int(f(x)));
    n=n+1;
end
display(x(n))

[Walter Roberson]

You have

syms x
f(x)= input('f(x)=');

and

x(1)=a;
x(n)=(x(n-1)-(f(x)/int(f(x))));

You are using x for two different purposes here: one as the symbolic variable to define f, and one as the record of the root.

Once you have assigned a definite value to x with x(1)=a then int(f(x)) is int() of f evaluated at that definite value, which would be indefinite int() of a constant, which is going to be x times the constant. Meanwhile f(x) is going to be the constant, so f(x)/int(f(x)) is going to be constant / (constant * x) which is going to be 1/x if the constant is non-zero, but is going to be NaN if the constant f(a) is 0.

[Wesam Hassan]

clc

syms x

f(x)= input('f(x)=');
a = input('a=');
b = input('b=');
n=1;
x=a;

y(1)=a;
y(n+1)=(y(n)-(f(x)/int(f(x))));

while y(n)~= y(n+1)
    x=y(n);
    n=n+1;
y(n+1)=(y(n)-(f(x)/int(f(x))));
end
display(y(n))
n=1;
x=b
y(1)=b;
y(n+1)=(y(n)-(f(x)/int(f(x))));
while y(n)~= y(n+1)
    x=y(n);
    n=n+1;
 y(n+1)=(y(n)-(f(x)/int(f(x))));
end
display(y(n))
n=1;
x=(a+b)/2
y(1)=(a+b)/2;
y(n+1)=(y(n)-(f(x)/int(f(x))));
while y(n)~= y(n+1)
    x=y(n);
    n=n+1;
    y(n+1)=(y(n)-(f(x)/int(f(x))));
end
display(y(n))

this code i replaced x(n) by y(n) which the error changed to become this

The following error occurred converting from sym to double:
Error using mupadmex
Error in MuPAD command: DOUBLE cannot convert the input expression into a
double array.

If the input expression contains a symbolic variable, use the VPA function
instead.

Error in NewtonMethod (line 12) y(n+1)=(y(n)-(f(x)/int(f(x))));

in th

[Walter Roberson]

Before the loop:

F = int(f(x));

After that,

y(n+1) = y(n) - f(y(n)) / F(y(n));

[Wesam Hassan]

do you mean that ? clc

syms x

f(x)= input('f(x)='); a = input('a='); b = input('b='); n=1; x=a; F = int(f(x));

y(1)=a; y(n+1)=(y(n)-(f(x)/F));

while y(n)~= y(n+1) x=y(n); n=n+1; y(n+1) = y(n) - f(y(n)) / F(y(n)); end if yes , the error didn't changed

[Walter Roberson]

No, you need to evaluate f and its integral at the current point y(n) so you need what I showed. However possibly you need to have used

F(x) = int(f(x))

[Wesam Hassan]

i do it but no changed in error the error what is meaning ? The following error occurred converting from sym to double: Error using mupadmex Error in MuPAD command: DOUBLE cannot convert the input expression into a double array.

If the input expression contains a symbolic variable, use the VPA function instead.

Error in NewtonMethod (line 13) y(n+1)=(y(n)-(f(x)/F(x)));

[Walter Roberson]

Where are you evaluating f and its integral at the current point? You are still using f(x) which gives you the formula for the function rather than evaluating the formula at the current point y(n)

I already posted the appropriate code.

[Wesam Hassan]

thanks so much i could solve the problem in my code :)