‘Ternary’ is an R package to allow the creation of ternary plots in the standard R graphics environment. I hope that it proves simple to use.

For simple use cases, generate Ternary plots using the point-and-click Shiny app:

install.packages('Ternary')
Ternary::TernaryApp()

For greater control over your plots, use the full R implementation.

Install the package with:

install.packages('Ternary')

Or if you want the latest development version of the package:

if (!require('devtools')) install.packages('devtools')
install_github('ms609/Ternary')

Once the package is installed, load it into the current R session with

library('Ternary')

There are two stages to creating a ternary plot: first, rendering the plot, styled as you like it and pointing in any of the four compass directions; secondly, adding data.

Create a blank plot

At its simplest, all you need to do is type

TernaryPlot()

The following charts show which corners are which, under different orientations:

par(mfrow = c(2, 2), mar = rep(0.5, 4))
for (dir in c('up', 'right', 'down', 'le')) {
  TernaryPlot(point = dir, atip = 'A', btip = 'B', ctip = 'C',
              alab = 'Aness', blab = 'Bness', clab = 'Cness')
  TernaryText(list(A = c(10, 1, 1), B = c(1, 10, 1), C = c(1, 1, 10)),
              col = cbPalette8[4], font = 2)
}

Plot two stylised plots side by side, and plot data

par(mfrow = c(1, 2), mar = rep(0.3, 4))
TernaryPlot(alab = "Redder \u2192", blab = "\u2190 Greener", clab = "Bluer \u2192",
            lab.col = c('red', 'darkgreen', 'blue'),
            point = 'right', lab.cex = 0.8, grid.minor.lines = 0,
            grid.lty = 'solid', col = rgb(0.9, 0.9, 0.9), grid.col = 'white', 
            axis.col = rgb(0.6, 0.6, 0.6), ticks.col = rgb(0.6, 0.6, 0.6),
            axis.rotate = FALSE,
            padding = 0.08)
# Colour the background:
cols <- TernaryPointValues(rgb)
ColourTernary(cols, spectrum = NULL)

# Add data points
data_points <- list(
  R = c(255, 0, 0), 
  O = c(240, 180, 52),
  Y = c(210, 222, 102),
  G = c(111, 222, 16),
  B = c(25, 160, 243),
  I = c(92, 12, 243),
  V = c(225, 24, 208)
)
AddToTernary(points, data_points, pch = 21, cex = 2.8, 
             bg = vapply(data_points, 
                         function (x) rgb(x[1], x[2], x[3], 128,
                                          maxColorValue = 255),
                         character(1))
             )
AddToTernary(text, data_points, names(data_points), cex = 0.8, font = 2)
legend('bottomright', 
       legend = c('Red', 'Orange', 'Yellow', 'Green'),
       cex = 0.8, bty = 'n', pch = 21, pt.cex = 1.8,
       pt.bg = c(rgb(255,   0,   0, 128, NULL, 255), 
                 rgb(240, 180,  52, 128, NULL, 255),
                 rgb(210, 222, 102, 128, NULL, 255),
                 rgb(111, 222,  16, 128, NULL, 255)),
       )


###
# Next plot:
###
TernaryPlot('Steam', 'Ice', 'Water', 
            grid.lines = 5, grid.lty = 'dotted',
            grid.minor.lines = 1, grid.minor.lty = 'dotted',
            point = 'West')
HorizontalGrid()
middle_triangle <- matrix(c(
  30, 40, 30,
  30, 30, 40,
  55, 20, 25
), ncol = 3, byrow = TRUE)
TernaryPolygon(middle_triangle, col = '#aaddfa', border = 'grey')
TernaryLines(list(c(0, 100, 0), middle_triangle[1, ]), col = 'grey')
TernaryLines(list(c(0, 0, 100), middle_triangle[2, ]), col = 'grey')
TernaryLines(list(c(100, 0, 0), middle_triangle[3, ]), col = 'grey')
TernaryArrows(c(20, 20, 60), c(30, 30, 40), length = 0.2, col = 'darkblue')

It is also possible to use cartesian coordinates to plot onto the graph.

By default, the plotting area is a 1x1 square.

par(mar = rep(0, 4)) # Reduce margins
TernaryPlot(point = 'right', clockwise = FALSE)
cat("X range in this orientation:", TernaryXRange())
## X range in this orientation: -0.0669873 0.9330127
cat("Y range in this orientation:", TernaryYRange())
## Y range in this orientation: -0.5 0.5
arrows(x0 = 0.5, y0 = 0.4, x1 = sqrt(3)/2, y1 = 0.4, length = 0.1,
       col = cbPalette8[2])
text(x = mean(c(0.5, sqrt(3)/2)), y = 0.4, "Increasing X", pos = 3,
     col = cbPalette8[2])
text(x = 0.5, y = 0, "(0.5, 0)", col = cbPalette8[3])
text(x = 0.8, y = -0.5, "(0.8, -0.5)", col = cbPalette8[3])

Note the anticlockwise axis labelling on this plot, obtained using clockwise = FALSE.

Contours

A plot can be coloured and contoured according to the output of a mathematical expression:

par(mar = rep(0.2, 4))
TernaryPlot(alab = 'a', blab = 'b', clab = 'c')

FunctionToContour <- function (a, b, c) {
  a - c + (4 * a * b) + (27 * a * b * c)
}

values <- TernaryPointValues(FunctionToContour, resolution = 24L)
ColourTernary(values)
TernaryContour(FunctionToContour, resolution = 36L)