There are a few coding problems and then there are a few conceptual problems
Coding problems. See inline comments below
plot(S(:,1),S(:,2),'b','linewidth',2) ;
xlim([x1-1 x2+1]); ylim([y1-1 y3+1]);
plot(S(i,1),S(i,2),'Or','markersize',10);
Conceptual problem #1
Instead of plotting the circle on each iteration, just move its position using this general idea:
h = plot(0,0,'Or','markersize',10);
set(h,'XData',S(i,1),'YData',S(i,2))
Conceptual problem #2
This is where you have thing about the data you're plotting. There are two reasons the cirlce moves slower on the vertical sections than on the horizontal sections.
- The aspect ratio of your x and y axes are not equal. Look at the range of values along the x and y axes. The x axis range is about twice as large as the y axis range yet that doesn't show in the ratio of the width and height of the blue path. To fix that, equate the aspect ratio using axis equal.
- Each line segment has 50 points no matter what length the line is. The long horizontal lines have 50 segments and the short vertical lines have 50 points. Your animation moves one coordinate at a time so of course it will be slower on vertical segments than horizontal segments because the coordinates are a lot more dense on vertical segments.
How to proceed
I'd be happy to steer you in the right direction.
First, instead of using linspace to create the coordinates, use a fixed interval. For example, instead of
use
interval = 0.5;
x2 : interval : x1
and do that for all line segements so they all have the same interval.
Then the animation should smoothly travel along the path, provided that your aspect ratios are equal as mentioned above.
