jansen.carrot {agridat} | R Documentation

## Infestation of carrots by fly larvae

### Description

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.

### 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. http://doi.org/10.1111/j.1467-9574.1993.tb01414.x

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

### References

None.

### Examples

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

    require(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:
      # Not run because CRAN wants < 5 seconds per example.  This is close.
      require(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

    ## End(Not run)

[Package agridat version 1.16 Index]