Average daily weight gain of steers on different diets

Description

The AvgDailyGain data frame has 32 rows and 6 columns.

Format

This data frame contains the following columns:

Id

the animal number

Block

an ordered factor indicating the barn in which the steer was housed.

Treatment

an ordered factor with levels 0 < 10 < 20 < 30 indicating the amount of medicated feed additive added to the base ration.

adg

a numeric vector of average daily weight gains over a period of 160 days.

InitWt

a numeric vector giving the initial weight of the animal

Trt

the Treatment as a numeric variable

Source

Littel, R. C., Milliken, G. A., Stroup, W. W., and Wolfinger, R. D. (1996), SAS System for Mixed Models, SAS Institute (Data Set 5.3).

Examples

library(SASmixed)
data(AvgDailyGain)
options(
  contrasts = c(unordered = "contr.SAS", ordered = "contr.poly"))
## plot of adg versus Treatment by Block
coplot(adg ~ as.numeric(Treatment) | Block, data = AvgDailyGain,
       show = FALSE)
fm1Adg <- lme( adg ~ InitWt * Treatment - 1, 
      data = AvgDailyGain, random = ~ 1 | Block)
summary( fm1Adg ) # compare with output 5.1, p. 178
VarCorr( fm1Adg ) # show the variance component estimates
anova( fm1Adg )   # checking significance of terms
fm2Adg <- update( fm1Adg, adg ~ InitWt + Treatment )  # common slope model
summary( fm2Adg )
VarCorr( fm2Adg )
anova( fm2Adg )
summary( update( fm1Adg, adg ~ InitWt + Treatment - 1 ) )