how to sort Indices of a circle in a 3d plane clockwise?

Question

ELI 2014-1-28

0
链接

此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/113998-how-to-sort-indices-of-a-circle-in-a-3d-plane-clockwise

评论： ELI 2014-1-28

Hi,

I have a sort of dots circle in a 3d plane and I want all the indices of the dots to be arranged clockwise. the indices of the dots are attached. Do you know how to do that?

2 个评论
显示无隐藏无

Roger Stafford 2014-1-28

(Copied from http://www.mathworks.com/matlabcentral/newsreader/view_thread/333601):

In three dimensions the notion of clockwise versus counterclockwise loses its meaning. The notion of clockwise rotation is strictly a two-dimensional concept. It has the same indeterminacy as trying to distinguish between the two sides of an arbitrary three-dimensional plane. Which side is the "plus" side and which is the "minus" side?

Mischa Kim 2014-1-28

Good point, Roger. Mathematically absolutely correct. From an engineering perspective I would argue that there is a somewhat "obvious" (and therefore in that same sense mathematically not necessarily definable), acceptable solution to the problem.

请先登录，再进行评论。

请先登录，再回答此问题。

Answer 1

Mischa Kim 2014-1-28

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/113998-how-to-sort-indices-of-a-circle-in-a-3d-plane-clockwise#answer_122477

编辑：Mischa Kim 2014-1-28

From the x and y data (from ind.mat) compute the polar angles of the dots using atan2. Add the polar angles as the fourth row to the matrix. Then use the sort command to sort the dots in descending order (in terms of angles).