Invalid expression. Check for missing multiplication operator, missing or unbalanced delimiters, or other syntax error. To construct matrices, use brackets instead of parenthe

>> clc; clear all;

E=input('Epsilon değerini giriniz E: ');

max=20;

fstr = input('Fonksiyon değerini giriniz f(x):', 's');

syms x

fsym = str2sym(fstr);

f = matlabFunction(fsym, 'vars', x);

f1sym = diff(fsym) ;

f1 = matlabFunction(f1sym, 'vars', x) ;

for k=1:max

a=f1(x0);

if abs(a)<0.00001

disp('turevin değeri sıfıra çok yakın, algoritma durur')

break

end

x1=x0-f(x0)/f1(x0);

hata=abs(x1-x0);

x0=x1;

y=f(x0);

if(abs(y)<epsilon)

break

end

end

disp('root')

x1;

disp('error')

y;

disp('iteration')

k;

[Aleyna Dolar]

I want to show the approach to the result by using the newton raphson method with the function value entered by the user, but it gives an error, how do I solve it?

Answer 1

[DGM]

I don't see anything that would cause that error, but there are other errors.

clc; clf

fstr = 'sin(x)'; %input('Fonksiyon değerini giriniz f(x):', 's');
xguess = 2.8; % x0 is undefined
epsilon = 0.0001; %input('Epsilon değerini giriniz E: '); % E is unused (is this the same epsilon?)
maxsteps = 20; % you're overloading max().  it's not causing an error, but it's a bad idea

syms x
fsym = str2sym(fstr);
f = matlabFunction(fsym, 'vars', x);
f1sym = diff(fsym) ;
f1 = matlabFunction(f1sym, 'vars', x);
x0 = xguess; % just doing this so that the user's guess can be plotted later
for k=1:maxsteps
    a=f1(x0);
    if abs(a)<0.00001
        disp('turevin değeri sıfıra çok yakın, algoritma durur')
        break
    end
    x1=x0-f(x0)/f1(x0);
    hata=abs(x1-x0);
    x0=x1;
    y=f(x0);
    if(abs(y)<epsilon)
        break
    end
end

% you can use fprintf() to display dynamic text 
fprintf('Root identified at %f\n',x1)

Root identified at 3.141592

fprintf('Y-error %e\n',y)

Y-error 9.024789e-07

fprintf('Iteration number %d\n',k)

Iteration number 2

% visualize the initial and final values
fplot(f); hold on; grid on
plot([xguess x1],f([xguess x1]),'*')