Package required but not available: ‘maptools’

Packages suggested but not available for checking: 'rgdal', 'rgeos'

Imports includes 23 non-default packages.
Importing from so many packages makes the package vulnerable to any of
them becoming unavailable.  Move as many as possible to Suggests and
use conditionally.

See section ‘The DESCRIPTION file’ in the ‘Writing R Extensions’
manual.
Package required but not available: ‘maptools’

Packages suggested but not available for checking: 'rgdal', 'rgeos'

See section ‘The DESCRIPTION file’ in the ‘Writing R Extensions’
manual.