There are two ways you can use the C++ code
- creating a
Rcpp::cppFunction() - Linking to
sfheadersin a package
The first option works, but is a bit pointless because if you’re in R anyway you would probably just call the R functions.
The second option is the whole reason I build this library!
Linking to a package
The reason all the C++ code is in header files in
inst/include is so you can call this code from another
library. To do so
- Set the
LinkingTo
For example, here’s the Description
file of the gpx package I’m working on.
LinkingTo
- Include the
sfheadersheader files you need in a .cpp file
include
- call the functions
functions
These screenshots are taken from my gpx library. Feel free to have a look and see how I use them.
Using cppFunction
Here are some example cppFunction() calls you can use to
make various sf objects
sfg_POINT
cppFunction(
includes = '#include "sfheaders/sfg/sfg.hpp"'
, code = '
SEXP a_point( SEXP x ) {
return sfheaders::sfg::sfg_point( x );
}
'
, plugins = "cpp11"
, depends = c("geometries", "sfheaders")
)
## vector
a_point( c(1,3) )
# [,1] [,2]
# [1,] 1 3
# attr(,"class")
# [1] "XY" "POINT" "sfg"
## single-row matrix
a_point( matrix(c(1,2), ncol = 2) )
# [,1] [,2]
# [1,] 1 2
# attr(,"class")
# [1] "XY" "POINT" "sfg"
## single-row data.frame
a_point( data.frame(x = 1, y = 2) )
# [,1] [,2]
# [1,] 1 2
# attr(,"class")
# [1] "XY" "POINT" "sfg"sfc_MULTIPOINT
cppFunction(
includes = '
#include "sfheaders/sfc/multipoint/sfc_multipoint.hpp"
',
code = '
SEXP a_multipoint( SEXP x ) {
return sfheaders::sfc::sfc_multipoint( x );
}
'
, plugins = "cpp11"
, depends = c("geometries", "sfheaders")
)
x <- 1:2
a_multipoint( x )
# [[1]]
# [,1] [,2]
# [1,] 1 2
# attr(,"class")
# [1] "XY" "MULTIPOINT" "sfg"
#
# attr(,"n_empty")
# [1] 0
# attr(,"crs")
# $input
# [1] NA
#
# $wkt
# [1] NA
#
# attr(,"class")
# [1] "crs"
# attr(,"class")
# [1] "sfc_MULTIPOINT" "sfc"
# attr(,"precision")
# [1] 0
# attr(,"bbox")
# xmin ymin xmax ymax
# 1 2 1 2
# attr(,"class")
# [1] "bbox"
x <- matrix(c(1,2,3,4,5,6), ncol = 2)
a_multipoint( x )
# [[1]]
# [,1] [,2]
# [1,] 1 4
# [2,] 2 5
# [3,] 3 6
# attr(,"class")
# [1] "XY" "MULTIPOINT" "sfg"
#
# attr(,"n_empty")
# [1] 0
# attr(,"crs")
# $input
# [1] NA
#
# $wkt
# [1] NA
#
# attr(,"class")
# [1] "crs"
# attr(,"class")
# [1] "sfc_MULTIPOINT" "sfc"
# attr(,"precision")
# [1] 0
# attr(,"bbox")
# xmin ymin xmax ymax
# 1 4 3 6
# attr(,"class")
# [1] "bbox"
x <- data.frame(x = 1:3, y = 4:6)
a_multipoint( x )
# [[1]]
# [,1] [,2]
# [1,] 1 4
# [2,] 2 5
# [3,] 3 6
# attr(,"class")
# [1] "XY" "MULTIPOINT" "sfg"
#
# attr(,"n_empty")
# [1] 0
# attr(,"crs")
# $input
# [1] NA
#
# $wkt
# [1] NA
#
# attr(,"class")
# [1] "crs"
# attr(,"class")
# [1] "sfc_MULTIPOINT" "sfc"
# attr(,"precision")
# [1] 0
# attr(,"bbox")
# xmin ymin xmax ymax
# 1 4 3 6
# attr(,"class")
# [1] "bbox"sf_LINESTRING
cppFunction(
includes = '
#include "sfheaders/sf/linestring/sf_linestring.hpp"
',
code = '
SEXP a_linestring( SEXP x, SEXP geometry_columns, SEXP id_column ) {
return sfheaders::sf::sf_linestring( x, geometry_columns, id_column );
}
',
plugins = "cpp11",
depends = c("geometries", "sfheaders")
)
x <- 1:2
a_linestring( x, NULL, NULL )
# id geometry
# 1 1 1, 2
x <- matrix(c(1,2,3,4,5,6), ncol = 2)
a_linestring( x, NULL, NULL )
# id geometry
# 1 1 1, 2, 3, 4, 5, 6
x <- data.frame(x = 1:6, y = 4:9, id = c(rep(1,3), rep(2,3)))
a_linestring( x, NULL, "id" )
# id geometry
# 1 1 1, 2, 3, 4, 5, 6
# 2 2 4, 5, 6, 7, 8, 9
x <- data.frame(x = 1:6, y = 4:9, z = 8:10, id = c(rep(1,3), rep(2,3)))
a_linestring( x, c("x","y"), "id" )
# id geometry
# 1 1 1, 2, 3, 4, 5, 6
# 2 2 4, 5, 6, 7, 8, 9
a_linestring( x, c("x","y", "z"), "id" )
# id geometry
# 1 1 1, 2, 3, 4, 5, 6, 8, 9, 10
# 2 2 4, 5, 6, 7, 8, 9, 8, 9, 10