Creating simple parent index from list of edges and nodes

Hello I am trying to figure out best and fastest way to simplify edge lists into a single index which will be called the parent node index. I have a list of n 3d points and a n-1 x 2 matrix that details the edges that connect between these two points by their index in the list for example a simple 3d segment line would be detailed like xyzpositions =

   [23.9880   75.4550   61.0237
   23.7692   75.4716   61.0289
   23.5496   75.4765   61.0357
   23.3299   75.4773   61.0438
   23.1102   75.4793   61.0532
   22.8906   75.4847   61.0653
   22.6715   75.4984   61.0819]
 and the list of edges would read

edges = [

           1           2
           2           3
           4           3
           4           5
           5           6
           6           7]

The end result would end up being a n x 1 vector that reads [0 1 2 3 4 5 6] the first point is considered the root and set to 0 so that the arrays will be of equal length. Every method I have been trying, since I haven't perfected it yet uses a lot of for loops and I was hoping there was possibly a more eloquent solution that people already use, The segments are also not always this simple and sometimes two points can connect to the same point so the edges will have same endpoint. thanks!

Answer 1

[Yu Jiang]

Hi Bernard

As far as I know, there is no available tool in MATLAB that can help you create a list of parent nodes directly from the data of edges. There are a function nodepar in the wavelet toolbox (see http://www.mathworks.com/help/wavelet/ref/nodepar.html), and a function parent in the statistics toolbox (see http://www.mathworks.com/help/stats/classregtree.parent.html) that can be used to obtain the parent nodes if the data is first used to construct certain types of trees. However, I think they might not help much in the issue you are facing.

So, I would like to suggest you share some of the code you are currently using. Then, people on this forum may provide useful suggestions on how to improve the efficiency of your code through, for example, appropriate vetorization.

-Yu Jiang