I'm having a difficult time understanding the paradigm of Matlab classes vs compared to c++. I wrote code the other day, and I thought it should work. It did not... until I added
<handle
after the classdef.
So I have two classes, landmarks and robot, both are called from within the simulation class. This is the main loop of obj.simulation.animate() and it works, until I try to plot two things at once.
DATA.path is a record of all the places a robot has been on the map, and it's updated every time the position is updated.
When I try to plot it, by uncommenting the two marked lines below, I get this error:
??? Error using == set
Invalid handle object.
Error in == simulationsimulation.animate at 45
set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2));
%INITIALIZE GLOBALS
global DATA XX
XX = [obj.robot.x ; obj.robot.y];
DATA.i=1;
DATA.path = XX;
%Setup Plots
fig=figure;
xlabel('meters'), ylabel('meters')
set(fig, 'name', 'Phil''s AWESOME 80''s Robot Simulator')
xymax = obj.landmarks.mapSize*3;
xymin = -(obj.landmarks.mapSize*3);
l.lm=scatter([0],[0],'b+');
%"UNCOMMENT ME"l.pth= plot(0,0,'k.','markersize',2,'erasemode','background'); % vehicle path
axis([xymin xymax xymin xymax]);
%Simulation Loop
for n = 1:720,
%Calculate and Set Heading/Location
XX = [obj.robot.x;obj.robot.y];
store_data(XX);
if n == 120,
DATA.path
end
%Update Position
headingChange = navigate(n);
obj.robot.updatePosition(headingChange);
obj.landmarks.updatePerspective(obj.robot.heading, obj.robot.x, obj.robot.y);
%Animate
%"UNCOMMENT ME" set(l.pth, 'xdata', DATA.path(1,1:DATA.i), 'ydata', DATA.path(2,1:DATA.i));
set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2));
rectangle('Position',[-2,-2,4,4]);
drawnow
This is the classdef for landmarks
classdef landmarks <handle
properties
fixedPositions; %# positions in a fixed coordinate system. [ x, y ]
mapSize; %Map Size. Value is side of square
x;
y;
heading;
headingChange;
end
properties (Dependent)
apparentPositions
end
methods
function obj = landmarks(mapSize, numberOfTrees)
obj.mapSize = mapSize;
obj.fixedPositions = obj.mapSize * rand([numberOfTrees, 2]) .* sign(rand([numberOfTrees, 2]) - 0.5);
end
function apparent = get.apparentPositions(obj)
currentPosition = [obj.x ; obj.y];
apparent = bsxfun(@minus,(obj.fixedPositions)',currentPosition)';
apparent = ([cosd(obj.heading) -sind(obj.heading) ; sind(obj.heading) cosd(obj.heading)] * (apparent)')';
end
function updatePerspective(obj,tempHeading,tempX,tempY)
obj.heading = tempHeading;
obj.x = tempX;
obj.y = tempY;
end
end
end
To me, this is how I understand things. I created a figure l.lm that has about 100 xy points. I can rotate this figure by using
set(l.lm,'XData',obj.landmarks.apparentPositions(:,1),'YData',obj.landmarks.apparentPositions(:,2));
When I do that, things work. When I try to plot a second group of XY points, stored in DATA.path, it craps out and I can't figure out why.
