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_textsf() 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.
geom_textsf(
mapping = aes(),
data = NULL,
stat = "sf",
position = "identity",
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE,
...
)geom_labelsf(
mapping = aes(),
data = NULL,
stat = "sf",
position = "identity",
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE,
...
)
A Layer ggproto object that can be added to a plot.
Set of aesthetic mappings created by aes(). If specified and
inherit.aes = TRUE (the default), it is combined with the default mapping
at the top level of the plot. You must supply mapping if there is no plot
mapping.
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. A function can be created
from a formula (e.g. ~ head(.x, 10)).
The statistical transformation to use on the data for this
layer, either as a ggproto Geom subclass or as a string naming the
stat stripped of the stat_ prefix (e.g. "count" rather than
"stat_count")
Position adjustment, either as a string naming the adjustment
(e.g. "jitter" to use position_jitter), or the result of a call to a
position adjustment function. Use the latter if you need to change the
settings of the adjustment.
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().
Arguments passed on to geom_textpath, geom_labelpath
text_onlyA logical(1) indicating whether the path part should be
plotted along with the text (FALSE, the default). If TRUE, any
parameters or aesthetics relating to the drawing of the path will be
ignored.
gapA logical(1) which if TRUE, breaks the path into two sections
with a gap on either side of the label. If FALSE, the path is plotted
as a whole. Alternatively, if NA, the path will be broken if the string
has a vjust between 0 and 1, and not otherwise. The default for the label
variant is FALSE and for the text variant is NA.
uprightA logical(1) which if TRUE (default), inverts any text
where the majority of letters would upside down along the path, to improve
legibility. If FALSE, the path decides the orientation of text.
halignA character(1) describing how multi-line text should be
justified. Can either be "center" (default), "left" or "right".
offsetA unit object of length 1 to determine the
offset of the text from the path. If this is NULL (default), the vjust
parameter decides the offset. If not NULL, the offset argument
overrules the vjust setting.
parseA logical(1) which if TRUE, will coerce the labels into
expressions, allowing for plotmath syntax to be used.
straightA logical(1) which if TRUE, keeps the letters of a label
on a straight baseline and if FALSE (default), lets individual letters
follow the curve. This might be helpful for noisy paths.
paddingA unit object of length 1 to determine the
padding between the text and the path when the gap parameter trims the
path.
text_smoothinga numeric(1) value between 0 and 100 that smooths
the text without affecting the line portion of the geom. The default value
of 0 means no smoothing is applied.
richA logical(1) whether to interpret the text as html/markdown
formatted rich text. Default: FALSE. See also the rich text section of
the details in geom_textpath().
remove_longif TRUE, labels that are longer than their associated path will be removed.
label.paddingAmount of padding around label. Defaults to 0.25 lines.
label.rRadius of rounded corners. Defaults to 0.15 lines.
geom_textsf() uses a unique aesthetic: geometry, giving an
column of class sfc containing simple features data. There
are three ways to supply the geometry aesthetic:
Do nothing: by default geom_textsf() 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.
Most regular geoms, such as geom_point(), geom_path(),
geom_text(), geom_polygon() etc. will work fine with coord_sf(). However
when using these geoms, two problems arise. First, what CRS should be used
for the x and y coordinates used by these non-sf geoms? The CRS applied to
non-sf geoms is set by the default_crs parameter, and it defaults to
NULL, which means positions for non-sf geoms are interpreted as projected
coordinates in the coordinate system set by the crs parameter. This setting
allows you complete control over where exactly items are placed on the plot
canvas, but it may require some understanding of how projections work and how
to generate data in projected coordinates. As an alternative, you can set
default_crs = sf::st_crs(4326), the World Geodetic System 1984 (WGS84).
This means that x and y positions are interpreted as longitude and latitude,
respectively. You can also specify any other valid CRS as the default CRS for
non-sf geoms.
The second problem that arises for non-sf geoms is how straight lines
should be interpreted in projected space when default_crs is not set to NULL.
The approach coord_sf() takes is to break straight lines into small pieces
(i.e., segmentize them) and then transform the pieces into projected coordinates.
For the default setting where x and y are interpreted as longitude and latitude,
this approach means that horizontal lines follow the parallels and vertical lines
follow the meridians. If you need a different approach to handling straight lines,
then you should manually segmentize and project coordinates and generate the plot
in projected coordinates.
stat_sf_coordinates().
Other geom layers that place text on paths.
ggplot(waterways) +
geom_textsf(label = "Forth and Clyde Canal",
hjust = 0.62, vjust = -0.3, fill = "#E4E0A3") +
lims(x = c(-4.2, -3.9), y = c(55.9, 56))
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