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# Geometry/List of Points

Question

list of points
QUESTION: Hi Hussain,

Sorry for previous unclear question, my question is, is any method to create a list of points? if the first point is A, how to make sure for others points BCDE, B is the next point of A, then C is the next point after B and so on based on the attached pic become list A->B->C->D->E

Thanks

While I appreciate the clarification, your question is still rather vague; context is needed.  What creates the list of points?  A mathematical sequence?  A computer program?  Some random algorithm?  If you can name me a specific situation in which you need to do this, I can try to help, but as it stands there still is not much of a question here.

Regards,
Azeem

---------- FOLLOW-UP ----------

QUESTION: Hey again,

I am doing a computer program, actually here I am drawing a plane using triangles, for example if has 5 points ABCDE, it will draw three triangles (ABC, ACD, ADE), those three become a plane. Based on the pic, I have a list of five points ABCDE, all of the points can be at random position, and I set one of them become the first point of a new list, So then I need to sort the old list sequentially based on the pic, for example:

1. point A as first point, so the new list will be ABCDE
2. point B as first point, so the new list will be BCDEA
3. point E as first point, so the new list will be EABCD

So maybe you can help me how to sort the old list, if we see from the pic the points in the new list are ordered clockwise.

I hope you understand

Thanks

Hi Fendi,

Convert your list of points to polar coordinates (radius, angle).  Sort the points by angle.  Locate the first point, then add the remaining points in the sorted order, wrapping around the list if necessary.  For example, in your picture the sorted order by angle is ABCDE.  If C were the first point, you would take CDE, then wrap around the list to get A and B, for a final order of CDEAB.

I hope this is clear enough.  There are experts in computer science categories who can probably help you with implementation if you need.

Azeem

Geometry

Volunteer

#### Azeem Hussain

##### Expertise

I welcome your questions on algebra, 2D and 3D geometry, parabolic functions and conic sections, and any other mathematical queries you may have.

##### Experience

4 years as a drop-in and by-appointment tutor at Champlain College. Private tutor for dozens of clients over the past 8 years.

Publications
CALPHAD: Computer Coupling of Phase Diagrams and Thermochemistry

Education/Credentials
Bachelor of Science, Major Mathematics and Major Economics, McGill University, 2014. Diploma of Collegiate Studies; Pure and Applied Science, Champlain College Saint-Lambert, 2010.