Description Usage Arguments Details Value
The general process is to conservatively buffer query_polys
, identify the US counties
intersecting the buffered query_polys
, then query the local eBird database for records
occurring in these counties. This may seem inefficient compared to querying the database
directly with the precise desired buffer, and it may be, but it is often impracticable to
have the entire eBird database loaded into RAM. Thus, this function pares the eBird database
to a manageable size (provided you're not querying an unreasonably large area of interest)
prior to doing the precise extraction of records based on the query_polys
and any
associated buffers. The precise extraction of records occurs on a polygon-by-polygon basis to
avoid complications arising from eBird record assignment when buffered polygons overlap. Thus,
the same eBird record may occur in multiple polygons depending on the buffer specification.
1 2 3 |
query_polys |
|
ebird_sqlite |
character string file path to local eBird SQLite (.sqlite) database file |
table_name |
character string naming the table within |
buffers |
numeric vector (multiple buffers allowed) of the distance (km) from
|
which_polys |
character vector of polygon names in |
poly_id |
character string of the column in |
projection |
CURRENTLY NOT USED; character string of PROJ.4 projection arguments; see also
|
exclude |
logical indicating whether to exclude |
This function should also work, but is untested, with SpatialPointsDataFrame-class
or
SpatialLinesDataFrame-class
) if a buffer is provided.
As the function currently relies on US counties to query the local eBird database, it works only for US locations. This could be expanded quite easily, however, to apply in other locations (e.g., Canadian provinces, Mexican states, etc.).
The WGS 84 / UTM (northern hemisphere) projection within which to perform the precise eBird record extraction is estimated programmatically based on the centroid (latitude and longitude) of each polygon. This should work for all US locations and most of the rest of the planet with the exception of the area around the southwestern coast of Norway and Svalbard (but it's the least of our concerns at the moment).
a data.frame
of eBird records in the query_polys
plus any
associated buffers
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