‘ggtern’ is a software package for the statistical computing language R. It is an extension to ggplot2 [1] specifically for the plotting of ternary diagrams.

Ternary diagrams are Barycentric plots w/ three variables, and, they are commonly used within the fields of chemistry, petrology, mineralogy, metallurgy, materials-science, genetics and game-theory, amongst others. Whereas a simplex diagram is the general case for $k$, in $k+1$ dimensions, the ternary diagram is the specific case when $k=2$ (producing $k+1=3$ vertices).

With the exception of the work by Sean Mulcahy [2] and Darren Wilkinson [3], there are very few resources on the internet where ggplot2 [1] has been used as a platform for rendering such diagrams, ggtern attempts to bridge this gap, and has since been used within a number of publications as a direct result.

If you are familiar with the syntax of ggplot2, then using ggtern should be a breeze, without too much trouble, it is quite easy to produce publication quality ternary diagrams such as the one immediately below:

References

[1] H. Wickham, ggplot2: Elegant Graphics for Data Analysis, Springer-Verlag, 2009.
[Bibtex]
``````@Book{wickham,
Title = {ggplot2: Elegant Graphics for Data Analysis},
Author = {Wickham, Hadley},
Publisher = {Springer-Verlag},
Year = {2009},
Owner = {Nick Hamilton},
Timestamp = {20131123}
}``````
[2] S. R. Mulcahy, “Ternary Plots in R.”
[Bibtex]
``````@Electronic{mulcahy,
Title = {Ternary Plots in R},
Author = {Mulcahy, S.R.},
HowPublished = {Website},
Language = {English},
Url = {http://srmulcahy.github.io/2012/12/04/ternary-plots-r.html},
Owner = {Nick Hamilton},
Timestamp = {20131222}
}``````
[3] D. Wilkinson, “Ternary Plots in GGPLOT/R.”
[Bibtex]
``````@Electronic{wilkinson,
Title = {Ternary Plots in GGPLOT/R},
Author = {Wilkinson, D.},
HowPublished = {Website},
Language = {English},
Url = {http://wilkinsondarren.wordpress.com/2013/09/10/ternary-plots-in-ggplotr/},
Owner = {Nick Hamilton},
Timestamp = {20131222}
}``````