The existing text-based geom layers in ggplot2
(geom_text() and
geom_label()) are ideal for the majority of plots,
since typically textual annotations are short, straight and in line with the
axes of the plot. However, there are some occasions when it is useful to have
text follow a curved path. This may be to create or recreate a specific
visual effect, or it may be to label a circular / polar plot in a more
"natural" way.
geom_textpath(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE,
...,
lineend = "butt",
linejoin = "round",
linemitre = 10,
text_only = FALSE,
gap = NA,
upright = TRUE,
halign = "center",
offset = NULL,
parse = FALSE,
straight = FALSE,
padding = unit(0.05, "inch"),
text_smoothing = 0,
rich = FALSE,
arrow = NULL,
remove_long = FALSE
)geom_textline(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
na.rm = FALSE,
orientation = NA,
show.legend = NA,
inherit.aes = TRUE,
...,
lineend = "butt",
linejoin = "round",
linemitre = 10,
arrow = NULL
)
geom_labelpath(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE,
...,
lineend = "butt",
linejoin = "round",
linemitre = 10,
text_only = FALSE,
gap = FALSE,
upright = TRUE,
halign = "center",
offset = NULL,
parse = FALSE,
straight = FALSE,
padding = unit(0.05, "inch"),
text_smoothing = 0,
rich = FALSE,
label.padding = unit(0.25, "lines"),
label.r = unit(0.15, "lines"),
arrow = NULL,
remove_long = FALSE
)
geom_labelline(
mapping = NULL,
data = NULL,
stat = "identity",
position = "identity",
na.rm = FALSE,
show.legend = NA,
inherit.aes = TRUE,
...,
lineend = "butt",
linejoin = "round",
linemitre = 10,
text_only = FALSE,
gap = FALSE,
upright = TRUE,
halign = "center",
offset = NULL,
parse = FALSE,
straight = FALSE,
padding = unit(0.05, "inch"),
label.padding = unit(0.25, "lines"),
label.r = unit(0.15, "lines"),
arrow = NULL,
remove_long = 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.
It can also be a named logical vector to finely select the aesthetics to
display.
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
colour = "red" or size = 3. They may also be parameters
to the paired geom/stat.
Line end style (round, butt, square).
Line join style (round, mitre, bevel).
Line mitre limit (number greater than 1).
A 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.
A 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.
A 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.
A character(1) describing how multi-line text should be
justified. Can either be "center" (default), "left" or "right".
A 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.
A logical(1) which if TRUE, will coerce the labels into
expressions, allowing for plotmath syntax to be used.
A 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.
A unit object of length 1 to determine the
padding between the text and the path when the gap parameter trims the
path.
a 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.
A 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().
Arrow specification, as created by grid::arrow().
if TRUE, labels that are longer than their associated path will be removed.
The orientation of the layer. The default (NA) automatically determines the orientation from the aesthetic mapping. In the rare event that this fails it can be given explicitly by setting orientation to either "x" or "y". See the Orientation section for more detail.
Amount of padding around label. Defaults to 0.25 lines.
Radius of rounded corners. Defaults to 0.15 lines.
geom_textpath() understands the following aesthetics (required aesthetics are in bold):
x
y
label
alpha
angle
colour
family
fontface
group
hjust
linecolour
lineheight
linetype
linewidth
size
spacing
textcolour
vjust
In addition to aforementioned aesthetics, geom_labelpath() also understands:
boxcolour
boxlinetype
boxlinewidth
fill
The spacing aesthetic allows fine control of spacing
of text, which is called 'tracking' in typography.
The default is 0 and units are measured in 1/1000 em.
Numbers greater than zero increase the spacing,
whereas negative numbers decrease the spacing.
Learn more about setting these aesthetics
in vignette("ggplot2-specs").
There are limitations inherent in the plotting of text elements in ggplot2 due to the way that the underlying grid graphics handles text. A text string is dealt with as a zero-width object, and therefore the rotation and spacing of the letters making up the string can only be dealt with by treating each letter separately.
It is important to realise that the letters are only rotated, and do not undergo any change in shape. Thus, for example, large text appearing on convex curves will not be deformed so that individual letters are narrower at the bottom and wider at the top. Doing so would require reinterpreting the letters as polygons.
Another issue is that we may wish to use a short curved label on a much
longer path. Spacing the letters equally along the path would mean there is
too much space between the letters for the label to remain legible. A single
text string is therefore kept "together" according to the point size of the
text in geom_textpath(). This then leaves the problem of where on the
path the text should be placed. This can be dealt with by the aesthetic
mapping hjust, which allows the user to place the labels
at the desired position along the path, including separate positions for
each label.
A final point to note is that a path is usually a group-based geom (i.e.
a path typically comprises x, y points from two columns over several rows of
a data frame), whereas text labels can come from single rows in a data frame.
This means that if we have a data frame with an x column, a y column and a
grouping variable column, there can only be a single label for the group.
Typically, this will be the grouping variable itself (see the examples,
particularly those using the built-in iris data set.)
The rich text option (rich = TRUE) relies heavily on rich-text parsers
copied from the {gridtext} package. We thank Claus O. Wilke for
developing {gridtext} and allowing us to re-use his code under the
MIT licence. Currently, the supported HTML tags are <p>, <span>, <b>,
<strong>, <i>, <em>, <sub>, <sup> and <br>.
Other geom layers that place text on paths.
# Plot text along an arbitrary path
t <- seq(-1, 5, length.out = 1000) * pi
spiral <- data.frame(
x = rev(sin(t) * 1000:1),
y = rev(cos(t) * 1000:1),
s = seq(1, 10, length.out = 100),
text = paste(
"Like a circle in a spiral, like a wheel within a wheel,",
"never ending or beginning on an ever spinning reel"
)
)
ggplot(spiral, aes(x, y, label = text)) +
geom_textpath(size = 7, vjust = 2, linewidth = 0) +
coord_equal(xlim = c(-1500, 1500), ylim = c(-1500, 1500))
# Use geom_textline as a drop-in for geom_line
df <- data.frame(x = rep(1:100, 3),
y = sin(c(seq(0, pi, len = 100),
seq(pi, 2*pi, len = 100),
rep(0, 100))),
label = rep(c("y is increasing",
"y is falling",
"y is flat"), each = 100))
ggplot(df, aes(x, y, label = label, color = label)) +
geom_textline(size = 6) + theme(legend.position = "none")
# Rich text labels can contain a subset of HTML tags
label <- paste0(
"Indometacin (",
"C19H16",
"Cl",
"N",
"O4",
") concentration"
)
# These are interpreted when `rich = TRUE`
ggplot(Indometh, aes(time, conc)) +
geom_point() +
geom_labelpath(
label = label,
stat = "smooth", formula = y ~ x, method = "loess",
vjust = -3, size = 8, rich = TRUE
) +
scale_x_log10()
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