Infestation of carrots by fly larvae

Infestation of 16 carrot genotypes by fly larvae, comparing 2 treatments in 16 blocks.

Usage

data("jansen.carrot")

Format

A data frame with 96 observations on the following 5 variables.

trt

treatment

gen

genotype

block

block

n

number of carrots sampled per plot

y

number of carrots infested per plot

Details

This experiment was designed to compare different genotypes of carrots with respect to their resistance to infestation by larvae of the carrotfly.

There were 16 genotypes, 2 levels of pest-control treatments, conducted in 3 randomized complete blocks. About 50 carrots were sampled from each plot and evaluated. The data show the number of carrots and the number infested by fly larvae.

Used with permission of J. Jansen. Electronic version supplied by Miroslav Zoric.

Source

J. Jansen & J.A. Hoekstra (1993). The analysis of proportions in agricultural experiments by a generalized linear mixed model. Statistica Neerlandica, 47(3), 161-174. https://doi.org/10.1111/j.1467-9574.1993.tb01414.x

References

None.

Examples

if (FALSE) { # \dontrun{

library(agridat)
data(jansen.carrot)
dat <- jansen.carrot

libs(lattice)
dotplot(gen ~ y/n, data=dat, group=trt, auto.key=TRUE,
        main="jansen.carrot",
        xlab="Proportion of carrots infected per block", ylab="Genotype")

  # Not run because CRAN wants < 5 seconds per example.  This is close.
  libs(lme4)
  # Tentative model.  Needs improvement.
  m1 <- glmer(cbind(y,n-y) ~ gen*trt + (1|block),
              data=dat, family=binomial)
  summary(m1)
  # Todo: Why are these results different from Jansen?
  # Maybe he used ungrouped bernoulli data?  Too slow with 4700 obs  
} # }