[R-sig-Geo] nearest neighbor 3d point pattern

[Seth Myers]

I am having a problem understanding the question fully due to text
formatting, etc.

Is this what you are after?

You have a list (List1) of points and each point has an x,y, and z value
that places it somewhere in that 3-D coordinate system.  You also have a
second list of points (List2), also with x,y,Z values.  For the points in
List1, you would like to know the closest point in List2.  Is this the case? 
Now, is it the case that the coordinate system for List1 and List2 are the
same?  By the same, I mean that the origin (where x,y, and z values are all
equal to zero) is in the same location and the dimensions extend
identically.

Unless you are worried about time of execution and need a clever way to
speed up execution, this seems like the type of function that you could
write in a few hours or less.

Have you tried writing a function utilizing a simple nested for loop
structure and this was somehow not sufficient?  I imagine with several
billion points that the obvious way of doing what you'd like would take
quite a while and use of a large amount of computer resources.



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