Multi-environment trial of cereal with lodging data
Percent lodging is given for 32 genotypes at 7 environments.
A data frame with 224 observations on the following 3 variables.
envenvironment, 1-7
gengenotype, 1-32
ypercent lodged
This data is for the first year of a three-year study.
Used with permission of Chris Glasbey.
D. J. Allcroft and C. A. Glasbey, 2003. Analysis of crop lodging using a latent variable model. Journal of Agricultural Science, 140, 383–393. https://doi.org/10.1017/S0021859603003332
## Not run:
library(agridat)
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',]$sy <- .01
libs(lattice)
dotplot(env~y|gen, dat, as.table=TRUE,
xlab="Percent lodged (by genotype)", ylab="Variety",
main="allcroft.lodging")
# Tobit model
libs(AER)
m3 <- tobit(sy ~ 1 + gen + env, left=0, right=100, data=dat)
# Table 2 trial/variety means
preds <- expand.grid(gen=levels(dat$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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