Where is the error and how is the code correct?

% Sample data points
x = [1, 2, 3];
f = [2, 5, 10];

% Call the function for curve fitting
dividedDifferenceTable(x, f);

Divided Difference Table:
     1     2     3     0
     2     5     0     0
     3    10     0     0

Polynomial: f(x) = 3*sym_x - 1

Error using solution>dividedDifferenceTable
Unable to run the 'fevalJSON' function because it calls the 'input' function, which is not supported for this product offering.

function dividedDifferenceTable(x, f)
% Check if the number of data points is consistent
if length(x) ~= length(f)
    error('Number of data points must be the same for x and f.');
end

n = length(x) - 1; % Degree of polynomial
F = zeros(n + 1, n + 2); % Divided difference table

% Fill in the first two columns of the table
F(:, 1) = x';
F(:, 2) = f';

% Construct the divided difference table
for j = 3:n + 2
    for i = 1:n + 2 - j
        F(i, j) = (F(i + 1, j - 1) - F(i, j - 1)) / (F(i + j - 2, 1) - F(i, 1));
    end
end

% Display the divided difference table
disp('Divided Difference Table:');
disp(F);

% Print the polynomial
syms sym_x;
poly = F(1, 2);
for i = 2:n + 1
    term = F(1, i + 1);
    for j = 1:i - 1
        term = term * (sym_x - F(j, 1));
    end
    poly = poly + term;
end
disp(['Polynomial: f(x) = ' char(poly)]);

% Evaluate the function at any given x
x_val = input('Enter the value of x to evaluate f(x): ');
result = subs(poly, sym_x, x_val);
disp(['f(' num2str(x_val) ') = ' num2str(result)]);

% Evaluate the absolute error
true_value = input('Enter the true value of f(x): ');
error = abs(result - true_value);
disp(['Absolute Error: ' num2str(error)]);
end

[Dyuman Joshi]

Which error are you talking about? Are you running the script in a live editor?

[Mohammed]

the error in line 9, variable maight be used before it is defined>

i do not know how i can fixed it

Answer 1

[Sulaymon Eshkabilov]

Here is the corrected code:

% Sample data points
x = [1, 2, 3];
f = [2, 5, 10];

% Call the function for curve fitting
dividedDifferenceTable(x, f);

function dividedDifferenceTable(x, f)
% Check if the number of data points is consistent
if length(x) ~= length(f)
    error('Number of data points must be the same for x and f.');
end

n = length(x) - 1; % Degree of polynomial
F = zeros(n + 1, n + 2); % Divided difference table

% Fill in the first two columns of the table
F(:, 1) = x';
F(:, 2) = f';

% Construct the divided difference table
for j = 3:n + 2
    for i = 1:n + 2 - j
        F(i, j) = (F(i + 1, j - 1) - F(i, j - 1)) / (F(i + j - 2, 1) - F(i, 1));
    end
end

% Display the divided difference table
disp('Divided Difference Table:');
disp(F);

% Print the polynomial
syms sym_x;
poly = F(1, 2);
for i = 2:n + 1
    term = F(1, i + 1);
    for j = 1:i - 1
        term = term * (sym_x - F(j, 1));
    end
    poly = poly + term;
end
disp(['Polynomial: f(x) = ' char(poly)]);

% Evaluate the function at any given x
x_val = input('Enter the value of x to evaluate f(x): ');
result = subs(poly, sym_x, x_val);
fprintf('f(%f) = %f \n', [x_val, result])
% Evaluate the absolute error
true_value = input('Enter the true value of f(x):  ');
error = abs(result - true_value);
fprintf('Absolute Error = %f \n', error)
end

[Mohammed]

% Sample data points

x = [1, 2, 3];

f = [2, 5, 10];

% Call the function for curve fitting

dividedDifferenceTable(x, f);

function dividedDifferenceTable(x, f)

% Check if the number of data points is consistent

if length(x) ~= length(f)

error('Number of data points must be the same for x and f.');

end

n = length(x) - 1; % Degree of polynomial

F = zeros(n + 1, n + 2); % Divided difference table

% Fill in the first two columns of the table

F(:, 1) = x';

F(:, 2) = f';

% Construct the divided difference table

for j = 3:n + 2

for i = 1:n + 2 - j

F(i, j) = (F(i + 1, j - 1) - F(i, j - 1)) / (F(i + j - 2, 1) - F(i, 1));

end

end

% Display the divided difference table

disp('Divided Difference Table:');

disp(F);

% Print the polynomial

syms sym_x;

poly = F(1, 2);

for i = 2:n + 1

term = F(1, i + 1);

for j = 1:i - 1

term = term * (sym_x - F(j, 1));

end

poly = poly + term;

end

disp(['Polynomial: f(x) = ' char(poly)]);

% Evaluate the function at any given x

x_val = input('Enter the value of x to evaluate f(x): ');

result = subs(poly, sym_x, x_val);

fprintf('f(%f) = %f \n', [x_val, result])

% Evaluate the absolute error

true_value = input('Enter the true value of f(x): ');

error = abs(result - true_value);

fprintf('Absolute Error = %f \n', error)

end

[Mohammed]

your code still makes error

[Sulaymon Eshkabilov]

Are you using MATLAB envrionment? It works perfectly well - see the screen shot of the CW

[Sulaymon Eshkabilov]

Mohammed:

Make one code as I suggested in my answer in M-file editor or live editor, and then execute it.

[Sulaymon Eshkabilov]

Ok ? :)

[Mohammed]

[Sulaymon Eshkabilov]

The problem here is that your MATLAB does not have Symbolic MATH toolbox. The code is correct.

[Mohammed]

Thank you very much

[Sulaymon Eshkabilov]

Most welcome! Glad to be of some help :)