[Rd] Set operation generics

[Roger Bivand]

Interesting thread, but perhaps better moved elsewhere at some point?

The nb class is really only a list representing a by-row sparse matrix, one row per list component, with attributes and corner-case code to mark geometries with no neighbours for a given definition of neighbour. The set operations were contributed by Nicholas Lewin-Koh possibly in 2001, possibly before, but IIRC the question of generics was considered, but we didn't add standard generics ([, c, etc.). So although the underlying list class could be made a character vector, I think getting a valid nb object back out was the blocking point. It is worth raising as an issue in the spdep repo!

Roger

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Roger Bivand
Emeritus Professor
Norwegian School of Economics
Postboks 3490 Ytre Sandviken, 5045 Bergen, Norway
Roger.Bivand using nhh.no