Number of lambs born to 3 breeds on 3 farms

Usage

data("mead.lamb")

Format

A data frame with 36 observations on the following 4 variables.

farm: farm: F1, F2, F3
breed: breed: B1, B2, B3
lambclass: lambing class: L0, L1, L2, L3
y: count of ewes in class

Details

The data 'y' are counts of ewes in different lambing classes. The classes are number of live lambs per birth for 0, 1, 2, 3+ lambs.

Source

Roger Mead, Robert N Curnow, Anne M Hasted. 2002. Statistical Methods in Agriculture and Experimental Biology, 3rd ed. Chapman and Hall. Page 359.

References

None

Examples

if (FALSE) { # \dontrun{

library(agridat)
data(mead.lamb)
dat <- mead.lamb

# farm 1 has more ewes in lambclass 3
d2 <- xtabs(y ~ farm+breed+lambclass, data=dat)
mosaicplot(d2, color=c("lemonchiffon1","moccasin","lightsalmon1","indianred"),
           xlab="farm/lambclass", ylab="breed", main="mead.lamb")

names(dat) <- c('F','B','L','y') # for compactness
# Match totals in Mead example 14.6
libs(dplyr)
dat <- group_by(dat, F,B)
summarize(dat, y=sum(y))
##          F      B     y
##   <fctr> <fctr> <int>
## 1     F1      A   150
## 2     F1      B    46
## 3     F1      C    78
## 4     F2      A    72
## 5     F2      B    79
## 6     F2      C    28
## 7     F3      A   224
## 8     F3      B   129
## 9     F3      C    34


# Models
m1 <- glm(y ~ F + B + F:B, data=dat,
          family=poisson(link=log))
m2 <- update(m1, y ~ F + B + F:B + L)
m3 <- update(m1, y ~ F + B + F:B + L + B:L)
m4 <- update(m1, y ~ F + B + F:B + L + F:L)
m5 <- update(m1, y ~ F + B + F:B + L + B:L + F:L)

AIC(m1, m2, m3, m4, m5) # Model 4 has best AIC
##    df      AIC
## m1  9 852.9800
## m2 12 306.5457
## m3 18 303.5781
## m4 18 206.1520
## m5 24 213.8873

# Change contrasts for Miroslav
m4 <- update(m4,
             contrasts=list(F=contr.sum,B=contr.sum,L=contr.sum))
summary(m4)

# Match deviance table from Mead
libs(broom)
all <- do.call(rbind, lapply(list(m1, m2, m3, m4, m5), broom::glance))
all$model <- unlist(lapply(list(m1, m2, m3, m4, m5),
                               function(x) as.character(formula(x)[3])))
all[,c('model','deviance','df.residual')]
##                         model  deviance df.residual
## 1                 F + B + F:B 683.67257          27
## 2             F + B + L + F:B 131.23828          24
## 3       F + B + L + F:B + B:L 116.27069          18
## 4       F + B + L + F:B + F:L  18.84460          18
## 5 F + B + L + F:B + B:L + F:L  14.57987          12


if(0){
  # Using MASS::loglm
  libs(MASS)
  # Note: without 'fitted=TRUE', devtools::run_examples has an error
  m4b <- MASS::loglm(y ~ F + B + F:B + L + F:L, data = dat, fitted=TRUE)
  # Table of farm * class interactions. Match Mead p. 360
  round(coef(m4b)$F.L,2)
  fitted(m4b)
  resid(m4b)
  # libs(vcd)
  # mosaic(m4b, shade=TRUE,
  # formula = ~ F + B + F:B + L + F:L,
  # residual_type="rstandard", keep_aspect=FALSE)
}

} # }