get_geometry sets up an input DT with a 'geometry' column for spatsoc's
sf interface. The function expects a data.table with relocation data and
a coordinate reference system.
Usage
get_geometry(
DT = NULL,
coords = NULL,
crs = NULL,
output_crs = 4326,
geometry_colname = "geometry"
)Arguments
- DT
input data.table
- coords
character vector of X coordinate and Y coordinate column names. Note: the order is assumed X followed by Y column names.
- crs
numeric or character defining the coordinate reference system to be passed to sf::st_crs. For example,
crs = "EPSG:32736"orcrs = 32736.- output_crs
default 4326, the output crs to transform the input coordinates to with sf::st_transform. If output_crs is NULL or FALSE or matching the crs argument, the coordinates will not be transformed
- geometry_colname
default "geometry", to optionally set output name of simple feature geometry list column
Value
get_geometry returns the input DT appended with a
geometry column which represents the input coordinates
as a sfc (simple feature geometry list column). If the output_crs
was provided, the geometry will be transformed to the output_crs.
A message is returned when a column named geometry already exists in
the input DT, because it will be overwritten.
See details for appending outputs using modify-by-reference in the FAQ.
Details
The DT must be a data.table. If your data is a data.frame, you can
convert it by reference using data.table::setDT() or by reassigning using
data.table::data.table().
The coords argument expects the names of columns in DT which correspond
to the X and Y coordinates.
Examples
# Load data.table
library(data.table)
# Read example data
DT <- fread(system.file('extdata', 'DT.csv', package = 'spatsoc'))
# Get geometry
get_geometry(DT, coords = c('X', 'Y'), crs = 32736)
#> ID X Y datetime population
#> <char> <num> <num> <POSc> <int>
#> 1: A 715851.4 5505340 2016-11-01 00:00:54 1
#> 2: A 715822.8 5505289 2016-11-01 02:01:22 1
#> 3: A 715872.9 5505252 2016-11-01 04:01:24 1
#> 4: A 715820.5 5505231 2016-11-01 06:01:05 1
#> 5: A 715830.6 5505227 2016-11-01 08:01:11 1
#> ---
#> 14293: J 700616.5 5509069 2017-02-28 14:00:54 1
#> 14294: J 700622.6 5509065 2017-02-28 16:00:11 1
#> 14295: J 700657.5 5509277 2017-02-28 18:00:55 1
#> 14296: J 700610.3 5509269 2017-02-28 20:00:48 1
#> 14297: J 700744.0 5508782 2017-02-28 22:00:39 1
#> geometry
#> <sfc_POINT>
#> 1: POINT (35.5501 -40.57459)
#> 2: POINT (35.54978 -40.57506)
#> 3: POINT (35.55038 -40.57538)
#> 4: POINT (35.54977 -40.57558)
#> 5: POINT (35.54989 -40.57561)
#> ---
#> 14293: POINT (35.36908 -40.54486)
#> 14294: POINT (35.36915 -40.54489)
#> 14295: POINT (35.3695 -40.54297)
#> 14296: POINT (35.36894 -40.54306)
#> 14297: POINT (35.37068 -40.54741)
# Print
print(DT)
#> ID X Y datetime population
#> <char> <num> <num> <POSc> <int>
#> 1: A 715851.4 5505340 2016-11-01 00:00:54 1
#> 2: A 715822.8 5505289 2016-11-01 02:01:22 1
#> 3: A 715872.9 5505252 2016-11-01 04:01:24 1
#> 4: A 715820.5 5505231 2016-11-01 06:01:05 1
#> 5: A 715830.6 5505227 2016-11-01 08:01:11 1
#> ---
#> 14293: J 700616.5 5509069 2017-02-28 14:00:54 1
#> 14294: J 700622.6 5509065 2017-02-28 16:00:11 1
#> 14295: J 700657.5 5509277 2017-02-28 18:00:55 1
#> 14296: J 700610.3 5509269 2017-02-28 20:00:48 1
#> 14297: J 700744.0 5508782 2017-02-28 22:00:39 1
#> geometry
#> <sfc_POINT>
#> 1: POINT (35.5501 -40.57459)
#> 2: POINT (35.54978 -40.57506)
#> 3: POINT (35.55038 -40.57538)
#> 4: POINT (35.54977 -40.57558)
#> 5: POINT (35.54989 -40.57561)
#> ---
#> 14293: POINT (35.36908 -40.54486)
#> 14294: POINT (35.36915 -40.54489)
#> 14295: POINT (35.3695 -40.54297)
#> 14296: POINT (35.36894 -40.54306)
#> 14297: POINT (35.37068 -40.54741)