Smoothed conditional means are available in ggplot2 via geom_smooth. This geom layer simply adds a text label to each curve that follow the contour of this line when used as a drop-in replacement for geom_smooth

## Usage

geom_textsmooth(
mapping = NULL,
data = NULL,
stat = "smooth",
position = "identity",
...,
method = NULL,
formula = NULL,
na.rm = FALSE,
method.args = list(),
orientation = NA,
show.legend = NA,
inherit.aes = TRUE
)

geom_labelsmooth(
mapping = NULL,
data = NULL,
stat = "smooth",
position = "identity",
method = NULL,
formula = NULL,
na.rm = FALSE,
method.args = list(),
orientation = NA,
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), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

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)).

stat

Use to override the default connection between geom_smooth() and stat_smooth().

position

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

...

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. These can also be the following text-path parameters:

gap

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.

upright

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.

halign

A character(1) describing how multi-line text should be justified. Can either be "center" (default), "left" or "right".

offset

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.

parse

A logical(1) which if TRUE, will coerce the labels into expressions, allowing for plotmath syntax to be used.

straight

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.

padding

A unit object of length 1 to determine the padding between the text and the path when the gap parameter trims the path.

text_smoothing

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.

rich

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().

remove_long

if TRUE, labels that are longer than their associated path will be removed.

method

Smoothing method (function) to use, accepts either NULL or a character vector, e.g. "lm", "glm", "gam", "loess" or a function, e.g. MASS::rlm or mgcv::gam, stats::lm, or stats::loess. "auto" is also accepted for backwards compatibility. It is equivalent to NULL.

For method = NULL the smoothing method is chosen based on the size of the largest group (across all panels). stats::loess() is used for less than 1,000 observations; otherwise mgcv::gam() is used with formula = y ~ s(x, bs = "cs") with method = "REML". Somewhat anecdotally, loess gives a better appearance, but is $$O(N^{2})$$ in memory, so does not work for larger datasets.

If you have fewer than 1,000 observations but want to use the same gam() model that method = NULL would use, then set method = "gam", formula = y ~ s(x, bs = "cs").

formula

Formula to use in smoothing function, eg. y ~ x, y ~ poly(x, 2), y ~ log(x). NULL by default, in which case method = NULL implies formula = y ~ x when there are fewer than 1,000 observations and formula = y ~ s(x, bs = "cs") otherwise.

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

method.args

List of additional arguments passed on to the modelling function defined by method.

orientation

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.

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. It can also be a named logical vector to finely select the aesthetics to display.

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().

## Value

A Layer ggproto object that can be added to a plot.

## Aesthetics

geom_textdensity() understands the following aesthetics (required aesthetics are in bold):

• x

• label

• alpha

• angle

• colour

• family

• fontface

• group

• hjust

• linecolour

• lineheight

• linetype

• linewidth

• size

• spacing

• textcolour

• vjust

In addition to aforementioned aesthetics, geom_labeldensity() 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").

Other geom layers that place text on paths.

## Examples

ggplot(iris, aes(x = Sepal.Length, y = Petal.Length)) +
geom_point(alpha = 0.1) +
geom_textsmooth(aes(label = Species, colour = Species),
method = "loess", formula = y ~ x,
size = 7, linetype = 3, fontface = 2, linewidth = 1) +
scale_colour_manual(values = c("forestgreen", "deepskyblue4", "tomato4")) +
theme_bw() +
theme(legend.position = "none")