Invalid expression. Check for missing or extra characters

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John
John 2023-9-6
评论： Walter Roberson 2023-9-7
Ran in:
L = 3;
eta_0 = 1 % Initial value of eta
tol = 1e-5;
rho = 1;
max_iter = 100; % Maximum number of iterations
% Define the function Psi as a separate MATLAB function
function y = Psi(eta);
y = rho/2; % Implementation of the contraction mapping with coefficient rho = 1
end
% Step 2: Implement the iteration loop
iter = 1;
Function definitions in a script must appear at the end of the file.
Move all statements after the "Psi" function definition to before the first local function definition.
eta_n = eta_0;
delta_eta = [];
while iter <= max_iter
omega_n = 1 / (iter * (iter + 1));
zeta_n = 1 / (iter + 1);
vartheta_n = 1 / (iter + 1);
eta_n_plus_1 = vartheta_n * Psi((eta_n + eta_n_plus_1) / 2) + zeta_n * (eye(size(A)) - omega_n * A * J) * ((eta_n + eta_n_plus_1) / 2);
if norm(eta_n_plus_1 - eta_n) < tol
break;
end
delta_eta = [delta_eta, norm(eta_n_plus_1 - eta_n)];
eta_n = eta_n_plus_1;
iter = iter + 1;
end
% Step 4: Plot the convergence rate
figure;
plot(1:length(delta_eta), delta_eta);
xlabel('Iteration number');
ylabel('||eta_{n+1} - eta_n||');
% Step 5: Generate the table of number of iterations
iter_vec = 1:iter;
eta_vec = [eta_0, eta_n];
table_data = [iter_vec' eta_vec'];
% Step 6: Display the table and plot
disp('Table of number of iterations:');
disp(table_data);
% Plot the convergence rate graph
  6 个评论
显示 4更早的评论
John
John 2023-9-6
This is what i always encounter
Error: File: untitled5.m Line: 19 Column: 1
Function definitions in a script must appear at the end of the file.
Move all statements after the "Psi" function definition to before the first local function definition.
Torsten
Torsten 2023-9-6
编辑：Torsten 2023-9-6
@Stephen23 already told you what to do:
Move
% Define the function Psi as a separate MATLAB function
function y = Psi(eta);
y = rho/2; % Implementation of the contraction mapping with coefficient rho = 1
end
to the end of your script and define the unknown variable "rho" therein. Why don't you use "eta" if you supply it as input to the function ?

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回答（1 个）

Walter Roberson
Walter Roberson 2023-9-6
Ran in:
Doing what the error message says to do fixes that error... exposing other errors.
L = 3;
eta_0 = 1 % Initial value of eta
eta_0 = 1
tol = 1e-5;
rho = 1;
max_iter = 100; % Maximum number of iterations
% Step 2: Implement the iteration loop
iter = 1;
eta_n = eta_0;
delta_eta = [];
while iter <= max_iter
omega_n = 1 / (iter * (iter + 1));
zeta_n = 1 / (iter + 1);
vartheta_n = 1 / (iter + 1);
eta_n_plus_1 = vartheta_n * Psi((eta_n + eta_n_plus_1) / 2) + zeta_n * (eye(size(A)) - omega_n * A * J) * ((eta_n + eta_n_plus_1) / 2);
if norm(eta_n_plus_1 - eta_n) < tol
break;
end
delta_eta = [delta_eta, norm(eta_n_plus_1 - eta_n)];
eta_n = eta_n_plus_1;
iter = iter + 1;
end
Unrecognized function or variable 'eta_n_plus_1'.
% Step 4: Plot the convergence rate
figure;
plot(1:length(delta_eta), delta_eta);
xlabel('Iteration number');
ylabel('||eta_{n+1} - eta_n||');
% Step 5: Generate the table of number of iterations
iter_vec = 1:iter;
eta_vec = [eta_0, eta_n];
table_data = [iter_vec' eta_vec'];
% Step 6: Display the table and plot
disp('Table of number of iterations:');
disp(table_data);
% Plot the convergence rate graph
% Define the function Psi as a separate MATLAB function
function y = Psi(eta);
y = rho/2; % Implementation of the contraction mapping with coefficient rho = 1
end
  2 个评论
John
John 2023-9-7
Ran in:
Can you also check. I try all kind of means and this is what am facing
L = 3;
eta_0 = 1 % Initial value of eta
tol = 1e-5;
rho = 1;
max_iter = 100; % Maximum number of iterations
iter = 1:max_iter;
eta_n = eta_0;
delta_eta = [];
% Define the function Psi as a separate MATLAB function
function y = Psi(eta);
y = rho/2; % Implementation of the contraction mapping with coefficient rho = 1
end
% Step 2: Implement the iteration loop
while iter <= max_iter
Function definitions in a script must appear at the end of the file.
Move all statements after the "Psi" function definition to before the first local function definition.
omega_n = 1 / (iter * (iter + 1));
zeta_n = 1 / (iter + 1);
vartheta_n = 1 / (iter + 1);
eta_(n+1) = vartheta_n * Psi((eta_n + eta_(n+1)) / 2) + zeta_n * (eye(size(A)) - omega_n * A * J) * ((eta_n + eta_(n+1)) / 2);
if norm(eta_(n+1) - eta_n) < tol
break;
end
delta_eta = [delta_eta, norm(eta_(n+1) - eta_n)];
eta_n = eta_(n+1);
iter = iter + 1;
end
% Step 4: Plot the convergence rate
figure;
plot(1:length(delta_eta), delta_eta);
xlabel('Iteration number');
ylabel('||eta_{n+1} - eta_n||');
% Step 5: Generate the table of number of iterations
iter_vec = 1:iter;
eta_vec = [eta_0, eta_n];
table_data = [iter_vec' eta_vec'];
% Step 6: Display the table and plot
disp('Table of number of iterations:');
disp(table_data);
% Plot the convergence rate graph
Walter Roberson
Walter Roberson 2023-9-7
Ran in:
If you have a specific reason for not moving the function definition like I showed, then you must use nested functions.
I also had to convert a number of * to .* and a number of / into ./ in order to be able to handle the fact that you are defining iter as a vector 1:max_iter . (I recommend firmly that you re-consider whether iter should be a vector or a scalar.)
draw_my_plots();
eta_0 = 1
Unrecognized function or variable 'eta_'.

Error in solution>draw_my_plots (line 31)
eta_(n+1) = vartheta_n * Psi((eta_n + eta_(n+1)) / 2) + zeta_n * (eye(size(A)) - omega_n * A * J) * ((eta_n + eta_(n+1)) / 2);
%an outer function is needed in order to be permitted to define a nested
%function. A nested function is needed in order to be able to access the
%rho variable inside Psi
function draw_my_plots
L = 3;
eta_0 = 1 % Initial value of eta
tol = 1e-5;
rho = 1;
max_iter = 100; % Maximum number of iterations
iter = 1:max_iter;
eta_n = eta_0;
delta_eta = [];
% Define the function Psi as a separate MATLAB function
function y = Psi(eta);
y = rho/2; % Implementation of the contraction mapping with coefficient rho = 1
end
% Step 2: Implement the iteration loop
while iter <= max_iter
omega_n = 1 ./ (iter .* (iter + 1));
zeta_n = 1 ./ (iter + 1);
vartheta_n = 1 ./ (iter + 1);
eta_(n+1) = vartheta_n * Psi((eta_n + eta_(n+1)) / 2) + zeta_n * (eye(size(A)) - omega_n * A * J) * ((eta_n + eta_(n+1)) / 2);
if norm(eta_(n+1) - eta_n) < tol
break;
end
delta_eta = [delta_eta, norm(eta_(n+1) - eta_n)];
eta_n = eta_(n+1);
iter = iter + 1;
end
% Step 4: Plot the convergence rate
figure;
plot(1:length(delta_eta), delta_eta);
xlabel('Iteration number');
ylabel('||eta_{n+1} - eta_n||');
% Step 5: Generate the table of number of iterations
iter_vec = 1:iter;
eta_vec = [eta_0, eta_n];
table_data = [iter_vec' eta_vec'];
% Step 6: Display the table and plot
disp('Table of number of iterations:');
disp(table_data);
% Plot the convergence rate graph
end

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