What does + geom_*() mean?

ggplot(iris, mapping=aes(x=Sepal.Length, y=Sepal.Width)) +
  geom_point()

is a shortcut to

ggplot(iris, mapping=aes(x=Sepal.Length, y=Sepal.Width)) +
  layer(geom="point", stat="identity", position="identity")

• Usage of layer()

  layer(
    geom = NULL,
    stat = NULL,
    data = NULL,
    mapping = NULL,
    position = NULL,
    params = list(),
    inherit.aes = TRUE,
    check.aes = TRUE,
    check.param = TRUE,
    show.legend = NA,
    key_glyph = NULL,
    layer_class = Layer
  )
  

• Component and Defaults in ’layer'

  • Besides data and aesthetic mapping, there are 3 basic components, geom, stat and position.
  • The default settings¹:

  geom	Useful stats (default in bold)	Default position adjustment	Parameters (when used with given stat)
  blank	identity	identity	no parameters
  abline	abline	identity	slope, intercept, size, linetype, colour, alpha
  	identity	identity	slope, intercept, size, linetype, colour, alpha
  hline	hline	identity	yintercept, size, linetype, colour, alpha
  	identity	identity	y, yend, size, linetype, colour, alpha
  vline	vline	identity	xintercept, size, linetype, colour, alpha
  	identity	identity	x, xend, size, linetype, colour, alpha
  text	identity	identity	x, y, label, size, colour, alpha, hjust, vjust, parse
  point	identity	identity	x, y, size, shape, colour, fill, alpha, na.rm
  jitter	identity	jitter	x, y, size, shape, colour, fill, alpha, na.rm
  segment	identity	identity	x, xend, y, yend, size, linetype, colour, alpha, arrow
  line	identity	identity	group, x, y, size, linetype, colour, alpha, arrow
  bar	identity	stack	x, y, size, linetype, colour, fill, alpha, weight(?) ???
  	bin	stack	x, y, size, linetype, colour, fill, alpha, weight(?) ???
  histogram	alias for geom_bar
  area	identity	stack	group, x, y, size, linetype, colour, fill, alpha, na.rm
  ribbon	identity	identity	group, x, ymin, ymax, size, linetype, colour, fill, alpha, na.rm
  linerange	identity	identity	x, ymin, ymax, size, linetype, colour, alpha
  pointrange	identity	identity	x, y, ymin, ymax, size, shape, linetype, colour, fill, alpha
  errorbar	identity	identity	x, ymin, ymax, size, linetype, colour, alpha, width
  errorbarh	identity	identity	x, xmin, xmax, y, size, linetype, colour, alpha, height
  crossbar	identity	identity	x, y, ymin, ymax, size, linetype, colour, fill, alpha, width, fatten
  boxplot	identity	dodge	x, ymin, lower, middle, upper, ymax, size, colour, fill, alpha, weight(?), width(?), outliers(?), outlier.size, outlier.shape, outlier.colour ???
  	boxplot	dodge	x, ymin, lower, middle, upper, ymax, size, colour, fill, alpha, weight(?), width(?), outliers(?), outlier.size, outlier.shape, outlier.colour ???
  path	identity	identity	group, x, y, size, linetype, colour, alpha, na.rm, arrow, linemitre, linejoin, lineend
  polygon	identity	identity	group, x, y, size, linetype, colour, fill, alpha
  rect	identity	identity	xmin, xmax, ymin, ymax, size, linetype, colour, fill, alpha
  rug	identity	identity	x, y, size, linetype, colour, alpha
  step	identity	identity	group, x, y, size, linetype, colour, alpha, direction
  bin2d	identity	identity	xmin, xmax, ymin, ymax, size, linetype, colour, fill, alpha, weight(?) ???
  	bin2d	identity	xmin, xmax, ymin, ymax, size, linetype, colour, fill, alpha, weight(?) ???
  tile	identity	identity	x, y, size, linetype, colour, fill, alpha
  hex	identity	identity	x, y, size, colour, fill, alpha
  	binhex	identity	x, y, size, colour, fill, alpha
  density	identity	identity	group, x, y, size, linetype, colour, fill, alpha, weight(?) ???
  	density	identity	group, x, y, size, linetype, colour, fill, alpha, weight(?) ???
  density2d	identity	identity	group, x, y, size, linetype, colour, alpha, weight(?), na.rm, arrow, linemitre, linejoin, lineend ???
  	density2d	identity	group, x, y, size, linetype, colour, alpha, weight(?), na.rm, arrow, linemitre, linejoin, lineend ???
  contour	identity	identity	group, x, y, size, linetype, colour, alpha, weight(?), na.rm, arrow, linemitre, linejoin, lineend ???
  	contour	identity	group, x, y, size, linetype, colour, alpha, weight(?), na.rm, arrow, linemitre, linejoin, lineend ???
  freqpoly	identity	identity	group, x, y, size, linetype, colour, alpha, weight(?) ???
  	bin	identity	group, x, y, size, linetype, colour, alpha, weight(?) ???
  quantile	identity	identity	group, x, y, size, linetype, colour, alpha, na.rm, arrow, linemitre, linejoin, lineend
  	quantile	identity	group, x, y, size, linetype, colour, alpha, weight, quantiles, formula, xseq, method, na.rm, arrow, linemitre, linejoin, lineend
  smooth	identity	identity	group, x, y, ymin, ymax, size, linetype, colour, fill, alpha
  	smooth	identity	group, x, y, size, linetype, colour, fill, alpha, weight

• Annotations (a special type of layer)

  Annotations don’t inherit global settings from the plot. They are used to add fixed reference data to plots.

Last modified on 2023-11-01