R package compositions:Compositional data analysis with R and the package compositions. This paper is a hands-on introduction and shows how to perform basic tasks in the analysis of compositional data following {it J. Aitchison}’s philosophy [The statistical analysis of compositional data. London-New York: Chapman and Hall (1986; Zbl 0688.62004)] within the statistical package `$R$’ and using a contributed package (called `compositions’), which is devoted specially to compositional data analysis. The studied asks are: descriptive statistics and plots (ternary diagrams, boxplots), principal component analysis (using biplots), cluster analysis with Aitchison distance, analysis of variance (ANOVA) of a dependent composition, some transformations and operations between compositions in the simplex.