Skye {MASS} | R Documentation

## AFM Compositions of Aphyric Skye Lavas

### Description

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

### Usage

    data(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

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

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, 219–253.

### 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], ...)
    }

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