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This set of geom, stat, and coord are used to visualise simple feature (sf)
objects. For simple plots, you will only need geom_sf
as it
uses stat_sf
and adds coord_sf
for you. geom_sf
is
an unusual geom because it will draw different geometric objects depending
on what simple features are present in the data: you can get points, lines,
or polygons.
stat_sf(mapping = NULL, data = NULL, geom = "rect",
position = "identity", na.rm = FALSE, show.legend = NA,
inherit.aes = TRUE, ...)geom_sf(mapping = aes(), data = NULL, stat = "sf",
position = "identity", na.rm = FALSE, show.legend = NA,
inherit.aes = TRUE, ...)
coord_sf(xlim = NULL, ylim = NULL, expand = TRUE, crs = NULL,
datum = sf::st_crs(4326), ndiscr = 100, default = FALSE)
The data to be displayed in this layer. There are three options:
If NULL
, the default, the data is inherited from the plot
data as specified in the call to ggplot()
.
A data.frame
, or other object, will override the plot
data. All objects will be fortified to produce a data frame. See
fortify()
for which variables will be created.
A function
will be called with a single argument,
the plot data. The return value must be a data.frame.
, and
will be used as the layer data.
The geometric object to use display the data
Position adjustment, either as a string, or the result of a call to a position adjustment function.
If FALSE
, the default, missing values are removed with
a warning. If TRUE
, missing values are silently removed.
logical. Should this layer be included in the legends?
NA
, the default, includes if any aesthetics are mapped.
FALSE
never includes, and TRUE
always includes.
You can also set this to one of "polygon", "line", and "point" to override the default legend.
If FALSE
, overrides the default aesthetics,
rather than combining with them. This is most useful for helper functions
that define both data and aesthetics and shouldn't inherit behaviour from
the default plot specification, e.g. borders()
.
Other arguments passed on to layer()
. These are
often aesthetics, used to set an aesthetic to a fixed value, like
color = "red"
or size = 3
. They may also be parameters
to the paired geom/stat.
The statistical transformation to use on the data for this layer, as a string.
Limits for the x and y axes.
Limits for the x and y axes.
If TRUE
, the default, adds a small expansion factor to
the limits to ensure that data and axes don't overlap. If FALSE
,
limits are taken exactly from the data or xlim
/ylim
.
Use this to select a specific CRS. If not specified, will use the CRS defined in the first layer.
CRS that provides datum to use when generating graticules
number of segments to use for discretizing graticule lines; try increasing this when graticules look unexpected
Is this the default coordinate system? If FALSE
(the default),
then replacing this coordinate system with another one creates a message alerting
the user that the coordinate system is being replaced. If TRUE
, that warning
is suppressed.
geom_sf
uses a unique aesthetic: geometry
, giving an
column of class sfc
containg simple features data. There
are three ways to supply the geometry
aesthetic:
Do nothing: by default geom_sf
assumes it is stored in
the geometry
column.
Explicitly pass an sf
object to the data
argument.
This will use the primary geometry column, no matter what it's called.
Supply your own using aes(geometry = my_column)
Unlike other aesthetics, geometry
will never be inherited from
the plot.
coord_sf()
ensures that all layers use a common CRS. You can
either specify it using the CRS
param, or coord_sf
will
take it from the first layer that defines a CRS.
# NOT RUN {
if (requireNamespace("sf", quietly = TRUE)) {
nc <- sf::st_read(system.file("shape/nc.shp", package = "sf"), quiet = TRUE)
ggplot(nc) +
geom_sf(aes(fill = AREA))
# If not supplied, coord_sf() will take the CRS from the first layer
# and automatically transform all other layers to use that CRS. This
# ensures that all data will correctly line up
nc_3857 <- sf::st_transform(nc, "+init=epsg:3857")
ggplot() +
geom_sf(data = nc) +
geom_sf(data = nc_3857, colour = "red", fill = NA)
# Unfortunately if you plot other types of feature you'll need to use
# show.legend to tell ggplot2 what type of legend to use
nc_3857$mid <- sf::st_centroid(nc_3857$geometry)
ggplot(nc_3857) +
geom_sf(colour = "white") +
geom_sf(aes(geometry = mid, size = AREA), show.legend = "point")
# You can also use layers with x and y aesthetics: these are
# assumed to already be in the common CRS.
ggplot(nc) +
geom_sf() +
annotate("point", x = -80, y = 35, colour = "red", size = 4)
# Thanks to the power of sf, a geom_sf nicely handles varying projections
# setting the aspect ratio correctly.
library(maps)
world1 <- sf::st_as_sf(map('world', plot = FALSE, fill = TRUE))
ggplot() + geom_sf(data = world1)
world2 <- sf::st_transform(
world1,
"+proj=laea +y_0=0 +lon_0=155 +lat_0=-90 +ellps=WGS84 +no_defs"
)
ggplot() + geom_sf(data = world2)
}
# }
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