Crosshair for Axes in Eigenvector Methods.

The origin (coordinates 0,0) has a special interpretation in eigenvector methods: sites, species or variables at the centroid are average cases, and the point is more exceptional the further it is from the origin. Therefore crosshair of axes through the origin should be added to the ordination graph with eigenvector methods. Often it is forgotten, though. See the Example in geom_ordi_arrow() where the length of PCA biplot arrow shows how exceptional the species is in ordination.

Usage

geom_ordi_axis(lty = 3, ...)

Arguments

lty

Linetype.

...

other arguments passed to ggplot2::geom_hline() and ggplot2::geom_vline()

Value

Returns ggplot2 layers geom_hline and geom_vline.

See also

The underlying functions are ggplot2::geom_hline() and ggplot2::geom_vline().

Author

Jari Oksanen

Examples

library(vegan)
library(ggplot2)
data(dune, package = "vegan")
mod <- cca(dune)
## simple "autoplot" using ggplot2::geom_text
ordiggplot(mod) +
  geom_ordi_axis() +
  geom_text()