Unwanted line connecting last point of current plot to the starting one of the next plot

Question

Sam 2019-11-1

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/488681-unwanted-line-connecting-last-point-of-current-plot-to-the-starting-one-of-the-next-plot

评论： Sam 2019-11-1

Dear friends

I want to plot trajectories of different orbits in one plot. The starting point (Earth) of each orbit is the same while orbital parameters varry. Using the program below I am almost able to plot trajectories, but there are two main problems:

final point of each trajectory is connected undesirably to the starting point of the next trajectory.
Initial points which should be located on the same point differ in location.

Any improvement is appreciated.

Thanks for your sincere help in advance

% input datas (these datas are just for instance)
a = [100e6,120e6,130e6]; %semi major axes of different orbits
e = [0.7,0.8,0.9]; %eccentricity of different orbits
dtheta = [90*pi/180,150*pi/180,180*pi/180]; % difference between true anomalies of radius-vectors at final point
dtheta1 = 20*pi/180; % difference between true anomalies of radius-vectors at initial point
[x,y] = OrbitPlotter(a,e,dtheta,dtheta1);
return
function [x,y] = OrbitPlotter(a,e,dtheta,dtheta1)
ElNum = numel(a);
u = 1;
v = 1;
while v <= ElNum
    dt = dtheta1; % I reset delta theta to initial value for each trajectory
while dt <= dtheta(v)
x = a(v)*cos(dt);
y = (a(v)*sqrt(1-e(v)^2))*sin(dt);
w(u) = x;
z(u) = y;
dt = dt + pi/180;
u = u + 1;
end
plot(w,z)
hold on
% [w,z] = sort(w); I tried sorting but didn't help much.
v = v + 1;
end
end

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Answer 1

ME 2019-11-1

1
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/488681-unwanted-line-connecting-last-point-of-current-plot-to-the-starting-one-of-the-next-plot#answer_399312

编辑：ME 2019-11-1

在 MATLAB Online 中打开

a = [100e6,120e6,130e6]; %semi major axes of different orbits
e = [0.7,0.8,0.9]; %eccentricity of different orbits
dtheta = [90*pi/180,150*pi/180,180*pi/180]; % difference between true anomalies of radius-vectors at final point
dtheta1 = 20*pi/180; % difference between true anomalies of radius-vectors at initial point
figure;
[x,y] = OrbitPlotter(a,e,dtheta,dtheta1);
return
function [x,y] = OrbitPlotter(a,e,dtheta,dtheta1)
u = 1;
v = 1;
for v = 1:numel(a)
    dt = dtheta1; % I reset delta theta to initial value for each trajectory
    while dt <= dtheta(v)
        x = a(v)*cos(dt);
        y = (a(v)*sqrt(1-e(v)^2))*sin(dt);
        w(u,v) = x;
        z(u,v) = y;
        dt = dt + pi/180;
        u = u + 1;
    end
    w(w==0)=nan;
    v(v==0)=nan;
    plot(w(:,v),z(:,v))
    hold on
end
end

Here the w(w==0)=nan; and v(v==0)=nan; are to account for the fact that the different orbits produce different length arrays. This prevents the plots going to the origin at the end of the orbit.