agridat (version 1.23)

becker.chicken: Mating crosses of chickens

Description

Mating crosses of chickens

Usage

data("becker.chicken")

Format

A data frame with 45 observations on the following 3 variables.

male

male parent

female

female parent

weight

weight (g) at 8 weeks

Details

From a large flock White Rock chickens, five male sires were chosen and mated to each of three female dams, producing 3 female progeny. The data are body weights at eight weeks of age.

Becker (1984) used these data to demonstrate the calculation of heritability.

References

None

Examples

if (FALSE) {

  library(agridat)
  data(becker.chicken)
  dat <- becker.chicken
  
  libs(lattice)
  dotplot(weight ~ female, data=dat, group=male,
          main="becker.chicken - progeny weight by M*F",
          xlab="female parent",ylab="progeny weight",
          auto.key=list(columns=5))

  # Sums match Becker
  # sum(dat$weight)
  # aggregate(weight ~  male + female, dat, FUN=sum)

  # Variance components
  libs(lme4,lucid)
  m1 <- lmer(weight ~  (1|male) + (1|female), data=dat)
  # vc(m1)
  ## grp        var1 var2      vcov    sdcor
  ## 1   female (Intercept)  1096   33.1
  ## 2     male (Intercept)   776.8 27.87
  ## 3 Residual          5524   74.32

  # Calculate heritabilities
  # s2m <- 776  # variability for males
  # s2f <- 1095 # variability for females
  # s2w <- 5524 # variability within crosses
  # vp <- s2m + s2f + s2w # 7395
  # 4*s2m/vp # .42 male heritability
  #4*s2f/vp # .59 female heritability

}