Weight of cork samples on four sides of trees

The cork data gives the weights of cork borings of the trunk for 28 trees on the north (N), east (E), south (S) and west (W) directions.

Format

Data frame with 28 observations on the following 5 variables.

tree

tree number

dir

direction N,E,S,W

y

weight of cork deposit (centigrams), north direction

Source

C.R. Rao (1948). Tests of significance in multivariate analysis. Biometrika, 35, 58-79. https://doi.org/10.2307/2332629

References

K.V. Mardia, J.T. Kent and J.M. Bibby (1979) Multivariate Analysis, Academic Press.

Russell D Wolfinger, (1996). Heterogeneous Variance: Covariance Structures for Repeated Measures. Journal of Agricultural, Biological, and Environmental Statistics, 1, 205-230.

Examples

if (FALSE) { # \dontrun{

  library(agridat)
  data(box.cork)
  dat <- box.cork

  libs(reshape2, lattice)
  dat2 <- acast(dat, tree ~ dir, value.var='y')
  splom(dat2, pscales=3,
        prepanel.limits = function(x) c(25,100),
        main="box.cork", xlab="Cork yield on side of tree",
        panel=function(x,y,...){
          panel.splom(x,y,...)
          panel.abline(0,1,col="gray80")
        })


  ## Radial star plot, each tree is one line
  libs(plotrix)
  libs(reshape2)
  dat2 <- acast(dat, tree ~ dir, value.var='y')
  radial.plot(dat2, start=pi/2, rp.type='p', clockwise=TRUE,
              radial.lim=c(0,100), main="box.cork",
              lwd=2, labels=c('North','East','South','West'),
              line.col=rep(c("royalblue","red","#009900","dark orange",
                             "#999999","#a6761d","deep pink"),
                           length=nrow(dat2)))

  if(require("asreml", quietly=TRUE)) {  
    libs(asreml, lucid)
    
    # Unstructured covariance
    dat$dir <- factor(dat$dir)
    dat$tree <- factor(dat$tree)  
    dat <- dat[order(dat$tree, dat$dir), ]
    
    # Unstructured covariance matrix
    m1 <- asreml(y~dir, data=dat, residual = ~ tree:us(dir))
    
    lucid::vc(m1)
    
    # Note: 'rcor' is a personal function to extract the correlations
    # into a matrix format
    # round(kw::rcor(m1)$dir, 2)
    #        E      N      S      W
    # E 219.93 223.75 229.06 171.37
    # N 223.75 290.41 288.44 226.27
    # S 229.06 288.44 350.00 259.54
    # W 171.37 226.27 259.54 226.00
    
    # Note: Wolfinger used a common diagonal variance
    
    # Factor Analytic with different specific variances
    # fixme: does not work with asreml4
    # m2 <- update(m1, residual = ~tree:facv(dir,1))
    # round(kw::rcor(m2)$dir, 2)
    #       E       N      S      W
    # E 219.94 209.46 232.85 182.27
    # N 209.46 290.41 291.82 228.43
    # S 232.85 291.82 349.99 253.94
    # W 182.27 228.43 253.94 225.99
  }
  
} # }