+--------+-------------------+
| Skye   | R Documentation   |
+--------+-------------------+

AFM Compositions of Aphyric Skye Lavas
--------------------------------------

Description
~~~~~~~~~~~

The ``Skye`` data frame has 23 rows and 3 columns.

Usage
~~~~~

::

    Skye

Format
~~~~~~

This data frame contains the following columns:

``A``
    Percentage of sodium and potassium oxides.

``F``
    Percentage of iron oxide.

``M``
    Percentage of magnesium oxide.

Source
~~~~~~

R. N. Thompson, J. Esson and A. C. Duncan (1972) Major element chemical
variation in the Eocene lavas of the Isle of Skye. *J. Petrology*,
**13**, 219â€“253.

References
~~~~~~~~~~

J. Aitchison (1986) *The Statistical Analysis of Compositional Data.*
Chapman and Hall, p.360.

Venables, W. N. and Ripley, B. D. (2002) *Modern Applied Statistics with
S.* Fourth edition. Springer.

Examples
~~~~~~~~

::

    # ternary() is from the on-line answers.
    ternary <- function(X, pch = par("pch"), lcex = 1,
                        add = FALSE, ord = 1:3, ...)
    {
      X <- as.matrix(X)
      if(any(X < 0)) stop("X must be non-negative")
      s <- drop(X %*% rep(1, ncol(X)))
      if(any(s<=0)) stop("each row of X must have a positive sum")
      if(max(abs(s-1)) > 1e-6) {
        warning("row(s) of X will be rescaled")
        X <- X / s
      }
      X <- X[, ord]
      s3 <- sqrt(1/3)
      if(!add)
      {
        oldpty <- par("pty")
        on.exit(par(pty=oldpty))
        par(pty="s")
        plot(c(-s3, s3), c(0.5-s3, 0.5+s3), type="n", axes=FALSE,
             xlab="", ylab="")
        polygon(c(0, -s3, s3), c(1, 0, 0), density=0)
        lab <- NULL
        if(!is.null(dn <- dimnames(X))) lab <- dn[[2]]
        if(length(lab) < 3) lab <- as.character(1:3)
        eps <- 0.05 * lcex
        text(c(0, s3+eps*0.7, -s3-eps*0.7),
             c(1+eps, -0.1*eps, -0.1*eps), lab, cex=lcex)
      }
      points((X[,2] - X[,3])*s3, X[,1], ...)
    }

    ternary(Skye/100, ord=c(1,3,2))

