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RTree


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 -- Class: RTree

     An Octave native extension implementing the R-tree spatial index of
     Guttman-Green.  The code is an embedded version of librtree.

     Given a set or rectangles (or higher dimensional cuboids) and their
     associated ids, one can build an RTree using the ‘csv_read’ class
     method or repeated calls to the ‘add_rect’ instance method.  The
     former is more performant since it avoids routing the rectangles
     through the Octave-C interface.

     Once the RTree instance is created one can make spatial queries
     against it with the ‘search method’; one passes a rectangle to the
     method and it applies a user-supplied callback function to the ids
     of all of the input rectangles which intersect it.

     It may be convenient to serialise the RTree for faster loading, the
     library implements a custom binary format, BSRT (binary serialised
     R-tree) which can be written by ‘bsrt_write’ and read with the
     ‘bsrt_read’ class method.  One can also serialise to JSON, but this
     results in a much larger file (a factor of ten) and so
     correspondingly slow to read/write.  Useful, nevertheless, for
     debugging.

     All rectangles used in the library are simply arrays of floats, the
     lower value for each dimension, followed by the upper value for
     each dimension.  Thus

          [0, 0, 1, 2]

     is the rectangle with 0 ≤ x ≤ 1 and 0 ≤ y ≤ 2.  Upper and lower
     values may coincide (to create a line segment in 2-space, for
     example) but a lower value larger than the upper value will cause
     an error.

     It is anticipated that the ids passed to the library will be used
     as an index for application specific data to which this rectangle
     relates (its location in an array, or a DB id) but this is entirely
     at the discretion of the caller, the library makes no use of the
     value, treating it as payload.  In particular, the value may be
     non-unique and may be zero.  One should note that the id type used
     internally by the library is determined at compile-time (with the
     ‘RTREE_ID_TYPE’ variable) and by default this is a 64-bit unsigned
     integer.

 -- RTree: OBJ = RTree (DIM, SPLIT, NP)

     Create a new (empty) RTree instance.

     DIM
          The dimension of the tree to create, an integer greater than
          0;
     SPLIT
          A string indicating the splitting strategy, one of "linear",
          "quadratic" or "greene", default "quadratic".  The linear
          strategy is faster to build, the quadratic and Greene
          strategies produce better-quality R-trees which are faster to
          query.
     NP
          The number of nodes-per-page, default 0.  This value can
          affect performance quite dramatically, particularly build
          time.  A value which is too large would result in an
          infeasible branching factor for the R-tree and will cause the
          function to error.  A value of zero is permitted and the
          default; in this case the function will choose a good value
          based on heuristics.  You may get better performance for your
          use-case by manual experimentation, but zero is a good place
          to start.

     See also: RTree.csv_read, RTree.add_rect.


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An Octave native extension implementing the R-tree spatial index of
Guttman-G...



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RTreeStyle


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 -- Class: RTreeStyle

     A Ruby wrapper around RTree styles, used in PostScript plotting.

 -- RTreeStyle: OBJ = RTreeStyle ()

     Creates an empty ‘RTreeStyle’ object, one can subsequently call the
     instance method ‘json’

     See also: RTreeStyle.json_read, RTree.postscript.


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A Ruby wrapper around RTree styles, used in PostScript plotting.





