triplot: Plot Holmans triangle

Description

Plot Holmans triangle (an equilateral triangle used to depict trinomial distributions).

Usage

triplot(
  labels = c("(1,0,0)", "(0,1,0)", "(0,0,1)"),
  col = "black",
  lwd = 2,
  bgcolor = "gray90",
  gridlines = 0,
  grid_col = "white",
  grid_lty = 1,
  grid_lwd = 1,
  ...
)

Value

The (x,y) coordinates of the points plotted, if any.

Arguments

labels: Labels for the three corners (lower-right, top, lower-left).
col: Color of edges of triangle
lwd: Line width for edges of triangle
bgcolor: Background color for triangle
gridlines: Number of grid lines (if 0, no grid lines will be plotted)
grid_col: Color of grid lines
grid_lty: Line type of grid lines
grid_lwd: Line width of grid lines
...: Passed to plot().

Details

Plot of an equilateral triangle, in order to depict trinomial distributions. A trinomial distribution (that is, a trio of non-negative numbers that add to 1) is equated to a point in the triangle through the distances to the three sides. This makes use of the fact that for any point in an equilateral triangle, the sum of the distances to the three sides is constant. The triplot function creates an empty triangle for use with the related functions tripoints(), trilines(), triarrow().

Examples

Run this code

triplot()
x <- cbind(c(0.9, 0.05, 0.05), c(0.8, 0.1, 0.1), c(0.1, 0.9, 0), c(0, 0.9, 0.1))
tripoints(x, lwd=2, col=c("black","blue","red","green"), pch=16)
trilines(x, lwd=2, col="orange")
y <- cbind(c(0.05, 0.05, 0.9), c(0.25, 0.25, 0.5))
triarrow(y, col="blue", lwd=2, len=0.1)