How to add iterations in Newton Raphson code of Kepler Equation

function [E] = Kepler(M,e,tol)

% File Kepler.m solves Kepler Equation

% Input: M = Mean anomoly in radians

% e = Eccentricity

% tol = tolerance

% Output: E = Eccentric anomoly in radians

En = M; % Using M as the first guess

Ens = En - (En-e*sin(En) - M)/(1 - e*cos(En)); % Newton Raphson iteration

while(abs(Ens-En)>tol) % Setting the tolerance as limit for iteration

En = Ens; % establishing forward step of iteration

Ens = En- (En - e*sin(En) - M)/(1 - e*cos(En)); % Re-calculation of new step

end

E = Ens; % update E

Matlab version used: Matlab R2020b

The above code works to provide a value of E, but how do i answer below question with only two input variables and add iterations to the code?

Answer 1

[Alan Stevens]

Like this

M = 0.908;
e = 0.725;
tol = 10^-6;
[E, its] = Kepler(M,e,tol);

E = 1.6579 after one iteration

disp(['E = ' num2str(E) ' after ' num2str(its), ' iterations'])

E = 1.6317 after 4 iterations

function [E,its] = Kepler(M,e,tol)
% File Kepler.m solves Kepler Equation
% Input: M = Mean anomoly in radians
%        e = Eccentricity
%        tol = tolerance
% Output: E = Eccentric anomoly in radians
En = M;                                              % Using M as the first guess
Ens = En - (En-e*sin(En) - M)/(1 - e*cos(En));       % Newton Raphson iteration
its = 0;
while(abs(Ens-En)>tol)                               % Setting the tolerance as limit for iteration
    En = Ens;                                        % establishing forward step of iteration
    Ens = En- (En - e*sin(En) - M)/(1 - e*cos(En));  % Re-calculation of new step
    its = its+1;
    if its==1
      disp(['E = ' num2str(Ens) ' after one iteration'])  
    end
end
E = Ens;
end

[imran shaikh]

Thanks Alan, I will give it a try