Invalid expression. Check for missing or extra characters
显示 更早的评论
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;
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
Stephen23
2023-9-6
One obvious bug is the a function in the middle of a script rather than at the end:
What value do you expect eta_n_plus_1 to have on the first loop iteration? You refer to it before it has been defined.
Pooja Kumari
2023-9-6
rho is not passed as an input to the function psi()
Pooja Kumari
2023-9-6
Variable A and Variable J are not defined
Walter Roberson
2023-9-6
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
Your function takes a parameter named eta but ignores it and uses the value of rho which is not defined inside the function and is not passed as a parameter.
There are some cases in which a function can refer to variables that have been defined in another function -- but this only happens when a function is defined inside another function . You are defining a function inside a script rather than inside a function, and this kind of sharing is not permitted between scripts and functions.
You need to either pass rho to Psi, or else you need to use nested functions.
John
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 ?
回答（1 个）
Doing what the error message says to do fixes that error... exposing other errors.
L = 3;
eta_0 = 1 % Initial value of eta
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
% 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
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();
%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
类别
在 帮助中心 和 File Exchange 中查找有关 Image Segmentation 的更多信息
2023-9-7
Community Treasure Hunt
Find the treasures in MATLAB Central and discover how the community can help you!
Start Hunting!
Translated by 
