Interface to Geometry Engine - Open Source ('GEOS') using the C 'API'
for topology operations on geometries. The 'GEOS' library is external
to the package, and, when installing the package from source, must be
correctly installed first. Windows and Mac Intel OS X binaries are
provided on 'CRAN'. ('rgeos' >= 0.5-1): Up to and including 'GEOS'
3.7.1, topological operations succeeded with some invalid geometries
for which the same operations fail from and including 'GEOS' 3.7.2.
The 'checkValidity=' argument defaults and structure have been
changed, from default FALSE to integer default '0L' for 'GEOS' < 3.7.2
(no check), '1L' 'GEOS' >= 3.7.2 (check and warn). A value of '2L' is
also provided that may be used, assigned globally using
'set_RGEOS_CheckValidity(2L)', or locally using the 'checkValidity=2L'
argument, to attempt zero-width buffer repair if invalid geometries
are found. The previous default (FALSE, now '0L') is fastest and used
for 'GEOS' < 3.7.2, but will not warn users of possible problems
before the failure of topological operations that previously
succeeded.
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