robustbase (version 0.95-1)

carrots: Insect Damages on Carrots

Description

The damage carrots data set from Phelps (1982) was used by McCullagh and Nelder (1989) in order to illustrate diagnostic techniques because of the presence of an outlier. In a soil experiment trial with three blocks, eight levels of insecticide were applied and the carrots were tested for insect damage.

Usage

data(carrots, package="robustbase")

Format

A data frame with 24 observations on the following 4 variables.

success

integer giving the number of carrots with insect damage.

total

integer giving the total number of carrots per experimental unit.

logdose

a numeric vector giving log(dose) values (eight different levels only).

block

factor with levels B1 to B3

References

McCullagh P. and Nelder, J. A. (1989) Generalized Linear Models. London: Chapman and Hall.

Eva Cantoni and Elvezio Ronchetti (2001); JASA, and
Eva Cantoni (2004); JSS, see glmrob

Examples

data(carrots)
str(carrots)
plot(success/total ~ logdose, data = carrots, col = as.integer(block))
coplot(success/total ~ logdose | block, data = carrots)

## Classical glm
Cfit0 <- glm(cbind(success, total-success) ~ logdose + block,
             data=carrots, family=binomial)
summary(Cfit0)

## Robust Fit (see help(glmrob)) ....