Trace along specific direction of perimeter of plotted object

Consider the following gif:

As you can see, when I loop through the [x y] data, it doesn't pick a direction to travel around the object. How can I make my loop such that it travels a specific direction and returns to where it began? I thought about sorting the data, that didn't work though.

Thanks in advance!

Answer 1

[coldsnack]

Alright I figured it out. For any future people who has this problem use bwtraceboundary. It will return a matrix with the correctly sorted data to loop around the object.

Answer 2

[Ameer Hamza]

For gif, it appears that your data is something like this

x = [x1 x1 x2 x2 x3 x3 x4 x4 ....... xn xn]; % every element is repeated twice
y = [y1 y2 y3 y4 y5 y6 y7 y8 .......... yn]; $ y1 y3 y5 to lower line, y2 y4 y6 to upper line

you just need to rearrange your vectors

xNew = zeros(1, length(x));
yNew = zeros(1, length(y));

[~, index] = unique(x);

xNew(1:length(index)) = x(1:2:end);
x(1:2:end) = [];
xNew(length(index)+1:end) = x(end:-1:1);

yNew(1:length(index)) = y(1:2:end);
y(1:2:end) = [];
yNew(length(index)+1:end) = y(end:-1:1);

Try running this and plot using xNew and yNew.

[coldsnack]

Thank you for the response. I can't run it since t is not defined. What should t be?

[Ameer Hamza]

Oh! I was testing it before posting here and forgot to edit t, now check the edited code.

[coldsnack]

I get the error

 In an assignment  A(:) = B, the number of elements in A and B must be 
 the same.

For the line

 xNew(1:length(index)) = x(1:2:end);

I tried to check the size of the left and right side of the equal sign. The left side has size

 1    94

and the right side has size

 149     1

Maybe it's because every element of x can be repeated more than two times?

[Ameer Hamza]

Can you show you x and y vector. It appears that they don't follow this pattern

x = [x1 x1 x2 x2 x3 x3 x4 x4 ....... xn xn]; % every element is repeated twice
y = [y1 y2 y3 y4 y5 y6 y7 y8 .......... yn]; $ y1 y3 y5 to lower line, y2 y4 y6 to upper line

[coldsnack]

Thank you for the patience. I have attached the two coordinate vectors.

[coldsnack]

I figured it out, thank you for the help.