Lodging data from a multi-environment trial cereal crop

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Description

Percent lodging is given for 32 genotypes at 7 environments.

Format

A data frame with 224 observations on the following 3 variables.

env

environment factor, 1-7

gen

genotype factor, 1-32

y

percent lodged

Details

This data is for the first year of a three-year study.

Source

D. J. Allcroft and C. A. Glasbey, 2003. Analysis of crop lodging using a latent variable model. Journal of Agricultural Science, 140, 383–393.

Used with permission of Chris Glasbey.

Examples

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data(allcroft.lodging)
dat <- allcroft.lodging

# Transformation
dat$sy <- sqrt(dat$y)
# Variety 4 has no lodging anywhere, so add a small amount
dat[dat$env=='E5' & dat$gen=='G04',]$sy <- .01

require(lattice)
dotplot(env~y|gen, dat, as.table=TRUE,
        xlab="Percent lodged (by genotype)", ylab="Variety",
        main="allcroft.lodging")

# Tobit model
if(require(AER)){
  m3 <- tobit(sy ~ 1 + gen + env, left=0, right=100, data=dat)

  # Table 2 trial/variety means
  preds <- expand.grid(gen=levels(dat$gen), env=levels(dat$env))
  preds$pred <- predict(m3, newdata=preds)
  round(tapply(preds$pred, preds$gen, mean),2)
  round(tapply(preds$pred, preds$env, mean),2)

}

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