ggpmisc (version 0.3.9)

geom_linked_text: Linked Text

Description

Text geoms are useful for labelling plots. `geom_linked_text()` adds text to the plot and for nudged positions links the original location to the nudged text with a segment.

Usage

geom_linked_text(
  mapping = NULL,
  data = NULL,
  stat = "identity",
  position = "identity",
  ...,
  parse = FALSE,
  nudge_x = 0,
  nudge_y = 0,
  arrow = NULL,
  check_overlap = FALSE,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE
)

Arguments

mapping

Set of aesthetic mappings created by aes or aes_. If specified and inherit.aes = TRUE (the default), is combined with the default mapping at the top level of the plot. You only need to supply mapping if there isn't a mapping defined for the plot.

data

A data frame. If specified, overrides the default data frame defined at the top level of the plot.

stat

The statistical transformation to use on the data for this layer, as a string.

position

Position adjustment, either as a string, or the result of a call to a position adjustment function.

...

other arguments passed on to layer. There are three types of arguments you can use here:

• Aesthetics: to set an aesthetic to a fixed value, like colour = "red" or size = 3.

• Other arguments to the layer, for example you override the default stat associated with the layer.

• Other arguments passed on to the stat.

parse

If TRUE, the labels will be parsed into expressions and displayed as described in ?plotmath.

nudge_x, nudge_y

Horizontal and vertical adjustments to nudge the starting position of each text label. The units for nudge_x and nudge_y are the same as for the data units on the x-axis and y-axis.

arrow

specification for arrow heads, as created by arrow

check_overlap

If TRUE, text that overlaps previous text in the same layer will not be plotted. check_overlap takes place at draw time and in the order of the data, thus its action depends of the size at which the plot is drawn.

na.rm

If FALSE (the default), removes missing values with a warning. If TRUE silently removes missing values.

show.legend

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.

inherit.aes

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.

Under development

This is a very simple and preliminary version of a geom. I plan to add features like padding around text and points. I aim to make use of the new features of 'grid' in R >= 4.1.0 to keep the implementation as fast and simple as possible. Currently this geom does all drawing using at most two vectorized calls to 'grid' functions. As a temporary replacement of padding around text one can use 'slightly out-of-range' numeric values for justification as shown in the examples.

Alignment

You can modify text alignment with the `vjust` and `hjust` aesthetics. These can either be a number between 0 (right/bottom) and 1 (top/left) or a character (`"left"`, `"middle"`, `"right"`, `"bottom"`, `"center"`, `"top"`). There are two special alignments: `"inward"` and `"outward"`. Inward always aligns text towards the center, and outward aligns it away from the center.

Details

Note that when you resize a plot, text labels stay the same size, even though the size of the plot area changes. This happens because the "width" and "height" of a text element are 0. Obviously, text labels do have height and width, but they are physical units, not data units. For the same reason, stacking and dodging text will not work by default, and axis limits are not automatically expanded to include all text.

By default this geom uses `position_nudge_center()` which is backwards compatible with `position_nudge()` from 'ggplot2' but provides additional control on the direction of the nudging. In contrast to `position_nudge()`, `position_nudge_center()` and `position_nudge_line()` preserve the original coordinates.

Examples

# NOT RUN {
my.cars <- mtcars[c(TRUE, FALSE, FALSE, FALSE), ]
my.cars$name <- rownames(my.cars)
p <- ggplot(my.cars, aes(wt, mpg, label = name))

# default behavior is as for geon_text()
p + geom_linked_text()
# Avoid overlaps
p + geom_linked_text(check_overlap = TRUE)
# Change size of the label
p + geom_linked_text(size = 2.5)

# Use nudging
p +
  geom_point() +
  geom_linked_text(hjust = -0.04, nudge_x = 0.12) +
  expand_limits(x = 6.2)
p +
  geom_point() +
  geom_linked_text(hjust = -0.04, nudge_x = 0.12,
  arrow = arrow(length = grid::unit(1.5, "mm"))) +
  expand_limits(x = 6.2)
p +
  geom_point() +
  geom_linked_text(vjust = -0.5, nudge_y = 0.5)
p +
  geom_point() +
  geom_linked_text(hjust = -0.02, nudge_x = 0.1,
                   vjust = -0.2, nudge_y = 0.5)
p +
  geom_point() +
  geom_linked_text(angle = 90,
                   hjust = -0.04, nudge_y = 1,
                   arrow = arrow(length = grid::unit(1.5, "mm"))) +
  expand_limits(y = 40)

# Add aesthetic mappings
p +
  geom_point() +
  geom_linked_text(aes(colour = factor(cyl)),
                   angle = 90,
                   hjust = -0.04, nudge_y = 1,
                   arrow = arrow(length = grid::unit(1.5, "mm"))) +
  scale_colour_discrete(l = 40) +
  expand_limits(y = 40)

p + geom_linked_text(aes(size = wt)) +
    expand_limits(x = c(2, 6))
# Scale height of text, rather than sqrt(height)
p +
  geom_linked_text(aes(size = wt)) +
  scale_radius(range = c(3,6)) +
    expand_limits(x = c(2, 6))

# You can display expressions by setting parse = TRUE.  The
# details of the display are described in ?plotmath, but note that
# geom_linked_text uses strings, not expressions.
p +
  geom_linked_text(
    aes(label = paste(wt, "^(", cyl, ")", sep = "")),
    parse = TRUE
  )

# Add a text annotation
p +
  geom_linked_text() +
  annotate(
    "linked_text", label = "plot mpg vs. wt",
    x = 2, y = 15, size = 3, colour = "red"
  )  +
 expand_limits(x = c(1.5, 6))

# Justification -------------------------------------------------------------
df <- data.frame(
  x = c(1, 1, 2, 2, 1.5),
  y = c(1, 2, 1, 2, 1.5),
  text = c("bottom-left", "bottom-right", "top-left", "top-right", "center")
)
ggplot(df, aes(x, y)) +
  geom_linked_text(aes(label = text))
ggplot(df, aes(x, y)) +
  geom_linked_text(aes(label = text), vjust = "inward", hjust = "inward")

# }