geom_catenary {ggpointless}

Draw a catenary curve

Description

geom_catenary() draws a catenary curve which has a U-like shape, similar in appearance to a parabola, which it is not.

Usage

geom_catenary(
  mapping = NULL,
  data = NULL,
  stat = "catenary",
  position = "identity",
  ...,
  chainLength = NULL,
  show.legend = NA,
  inherit.aes = TRUE,
  na.rm = FALSE
)

stat_catenary(
  mapping = NULL,
  data = NULL,
  geom = "path",
  position = "identity",
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  chainLength = NULL,
  ...
)

Arguments

mapping

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.

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)).

position

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.

...

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.

chainLength

Length of chain between two points.

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().

na.rm

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

geom, stat

Use to override the default connection between geom_catenary and stat_catenary.

Details

If a flexible chain or rope is loosely hung between two fixed points, it is a curve called a catenary. Catenary, from Latin word catēna, means "chain".

Aesthetics

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

• x

• y

• alpha

• color

• group

• linetype

• linewidth

Examples

dat <- data.frame(
  x = c(0, 1, 2),
  y = c(1, 2, -3)
)

p <- ggplot(dat, aes(x, y))
p + geom_catenary() +
  ylim(-4, NA)

# use chainLength argument to change default behaviour
# if you pick a chain length that is too short, a straight line is
# drawn and a message about minimum chain length is shown
p + geom_catenary(chainLength = 10) +
  ylim(-4, NA)