How do I plot on the same figure from 2 functions?

Sorry if this has already been asked and answered, I couldn't find it.

I want to make a 3D plot the orbit of a SC around the Earth and have written a script to do that. I have also written a function to project the Earth but it doesn't map onto the figure correctly. Is there a way to plot onto the same figure from both the script and the function that is called?

Below is the main script:

positionData = data;
figure(1)
% Plot orbit in ECI reference
% Generation of a sphere
hold off
Earth3D(1)
hold on
plot3(positionData(:, 1), positionData(:, 2), positionData(:, 3),'o-r');
% grid; axis equal;
xlabel('X'); ylabel('Y'); zlabel('Z');
title('Orbit ECI (inertial) (m)')

The Earth3D function is intended to project the Earth:

function Earth3D(figure)
% Defines the Earth object and it's parameters as well as the plot size for the transformation.
[x,y,z] = sphere(1000);
xe=x.*6378.137;
ye=y.*6378.137;
ze=z.*6356.752;
[I,~] = imread('STK_map.jpg');
figure(figure)
hold on
warp(xe,ye,-ze,I);
% ax1 = gca;          %Creates object for the axis of the plot to allow it to be defined.
% ax1.YDir='normal';  %Defines y axis of the plot with + at the top.
axis equal;
xlabel('x'); ylabel('y'); zlabel('z');

I have also attached the 'data' function which just contains the spacecraft's position data, and the 'STK_map' for the Earth image.

Thank you for any help you can provide.

Answer 1

[Tommy]

When you name a variable in your function figure, you can no longer access the function figure(). For example:

>> figure = 1;
>> figure(figure)

ans =

     1

% no figure is created

That is likely your main problem.

It seems like warp just plots to the current axes. I would recommend working with handles. I think this could work:

positionData = data;
% Plot orbit in ECI reference
% Generation of a sphere
f = figure;
ax = axes(f, 'NextPlot', 'add');
Earth3D(ax)
plot3(ax, positionData(:, 1), positionData(:, 2), positionData(:, 3),'o-r');
% grid(ax, 'on'); axis(ax, 'equal');
xlabel(ax, 'X'); ylabel(ax, 'Y'); zlabel(ax, 'Z');
title(ax, 'Orbit ECI (inertial) (m)')

with your function defined like this:

function Earth3D(ax)
% Defines the Earth object and it's parameters as well as the plot size for the transformation.
[x,y,z] = sphere(1000);
xe=x.*6378.137;
ye=y.*6378.137;
ze=z.*6356.752;
[I,~] = imread('STK_map.jpg');
axes(ax) % make ax the current axes
warp(xe,ye,-ze,I);
% ax.YDir='normal';  %Defines y axis of the plot with + at the top.
axis(ax, 'equal');
%xlabel(ax, 'x'); ylabel(ax, 'y'); zlabel(ax, 'z');

[Fraser Scanlan]

It still seems to have the same problem. The Earth is plotted, then the orbit replaces it as opposed to being plotted on the same figure.

[Tommy]

With 'NextPlot' set to 'on', that shouldn't happen. If you save the axes limits before your call to plot3 and then restore the limits afterwards, you should see that your sphere is still there.

positionData = data;
% Plot orbit in ECI reference
% Generation of a sphere
f = figure;
ax = axes(f, 'NextPlot', 'add');
Earth3D(ax)
lims = axis(ax); % save limits
plot3(ax, positionData(:, 1), positionData(:, 2), positionData(:, 3),'o-r');
axis(ax, lims); % restore limits
% grid(ax, 'on'); axis(ax, 'equal');
xlabel(ax, 'X'); ylabel(ax, 'Y'); zlabel(ax, 'Z');
title(ax, 'Orbit ECI (inertial) (m)')

Are you sure that the data contained within positionData are compatible with the axes limits? It seems that you are plotting the red circles very far away from the globe.

[Fraser Scanlan]

You're right I was using the wrong scale, thank you for helping, it works now!

[Tommy]

Awesome, happy to help!