On this R-data statistics page, you will find information about the grouseticks data set which pertains to Data on red grouse ticks from Elston et al. 2001. The grouseticks data set is found in the lme4 R package. You can load the grouseticks data set in R by issuing the following command at the console data("grouseticks"). This will load the data into a variable called grouseticks. If R says the grouseticks data set is not found, you can try installing the package by issuing this command install.packages("lme4") and then attempt to reload the data. If you need to download R, you can go to the R project website. You can download a CSV (comma separated values) version of the grouseticks R data set. The size of this file is about 18,311 bytes.

Data on red grouse ticks from Elston et al. 2001

Description

Number of ticks on the heads of red grouse chicks sampled in the field (grouseticks) and an aggregated version (grouseticks_agg); see original source for more details

Usage

data(grouseticks)

Format

INDEX

(factor) chick number (observation level)

TICKS

number of ticks sampled

BROOD

(factor) brood number

HEIGHT

height above sea level (meters)

YEAR

year (-1900)

LOCATION

(factor) geographic location code

cHEIGHT

centered height, derived from HEIGHT

meanTICKS

mean number of ticks by brood

varTICKS

variance of number of ticks by brood

Details

grouseticks_agg is just a brood-level aggregation of the data

Source

Robert Moss, via David Elston

References

Elston, D. A., R. Moss, T. Boulinier, C. Arrowsmith, and X. Lambin. 2001. "Analysis of Aggregation, a Worked Example: Numbers of Ticks on Red Grouse Chicks." Parasitology 122 (05): 563-569. doi:10.1017/S0031182001007740. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=82701.

Examples

data(grouseticks)
## Figure 1a from Elston et al
par(las=1,bty="l")
tvec <- c(0,1,2,5,20,40,80)
pvec <- c(4,1,3)
with(grouseticks_agg,plot(1+meanTICKS~HEIGHT,
                  pch=pvec[factor(YEAR)],
                  log="y",axes=FALSE,
                  xlab="Altitude (m)",
                  ylab="Brood mean ticks"))
axis(side=1)
axis(side=2,at=tvec+1,label=tvec)
box()
abline(v=405,lty=2)
## Figure 1b
with(grouseticks_agg,plot(varTICKS~meanTICKS,
                  pch=4,
                  xlab="Brood mean ticks",
                  ylab="Within-brood variance"))
curve(1*x,from=0,to=70,add=TRUE)
## Model fitting
form <- TICKS~YEAR+HEIGHT+(1|BROOD)+(1|INDEX)+(1|LOCATION)
(full_mod1  <- glmer(form, family="poisson",data=grouseticks))

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Dataset imported from https://www.r-project.org.