How to compute eccentricity for elliptical

Question

Mohammed Alshehri 2017-2-6

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/323628-how-to-compute-eccentricity-for-elliptical

评论： Mohammed Alshehri 2017-2-6

test.m

how to make matlab compute eccentricity for elliptical figure that I am creating. I am creating elliptical using numerical method. See code below and attached.

clear all
clc
%* Set initial position and velocity of the comet.
r0 = 1 ;
v0 = pi;
r = [r0 0];  v = [0 v0];
%* Set physical parameters (mass, G*M)
GM = 4*pi^2;      % Grav. const. * Mass of Sun (au^3/yr^2)
mass = 1.;        % Mass of comet 
adaptErr = 1.e-4; % Error parameter used by adaptive Runge-Kutta
time = 0;
%* Loop over desired number of steps using specified
%  numerical method.
nStep = 1000;
tau = 0.001;
for iStep=1:nStep  
    %* Record position and energy for plotting.
    rplot(iStep) = norm(r);           % Record position for polar plot
    thplot(iStep) = atan2(r(2),r(1));
    tplot(iStep) = time;
    kinetic(iStep) = .5*mass*norm(v)^2;   % Record energies
    potential(iStep) = - GM*mass/norm(r);
% Euler-Cromer step
 accel = -GM*r/norm(r)^3;   
 v = v + tau*accel; 
 r = r + tau*v;             
 time = time + tau;     
   unwrap_theta=unwrap(thplot);
      if unwrap_theta(iStep) > 2*pi 
          break
      end
end
%* Graph the trajectory of the comet.
figure(1); clf;  % Clear figure 1 window and bring forward
q=polar(thplot,rplot,'-');  % Use polar plot for graphing orbit
xlabel('Distance (AU)');  grid;