StroupGLMM (version 0.3.0)

Exam7.2: Example 7.2 from Generalized Linear Mixed Models: Modern Concepts, Methods and Applications by Walter W. Stroup (p-219)

Description

Exam7.2 explains multifactor models with some factors qualitative and some quantitative(Equal slopes ANCOVA)

Author

1. Muhammad Yaseen ()

2. Adeela Munawar ()

References

1. Stroup, W. W. (2012). Generalized Linear Mixed Models: Modern Concepts, Methods and Applications. CRC Press.

@seealso DataSet7.2

Examples

library(emmeans)
library(car)
library(ggplot2)

data(DataSet7.2)
DataSet7.2$trt <- factor( x = DataSet7.2$trt )

##----ANCOVA(Equal slope Model)
Exam7.2fm1 <- aov(formula = y ~ trt*x, data = DataSet7.2)
car::Anova(mod = Exam7.2fm1 , type = "III")

##---ANCOVA(without interaction because of non significant slope effect)
Exam7.2fm2 <- aov(formula = y ~ trt + x, data    = DataSet7.2)
car::Anova(mod = Exam7.2fm2 , type = "III")

##---Ls means for 2nd model
emmeans(object  = Exam7.2fm2, specs = ~trt)

##---Anova without covariate
Exam7.2fm3 <- aov(formula = y ~ trt, data = DataSet7.2)
car::Anova(mod = Exam7.2fm3, type = "III")

##---Ls means for 3rd model
emmeans(object = Exam7.2fm3, specs = ~trt)

##---Box Plot of Covariate by treatment
Plot <-
   ggplot(
          data    = DataSet7.2
        , mapping = aes(x = factor(trt), y = x)
         )                 +
   geom_boxplot(width = 0.5) +
   coord_flip()            +
   geom_point()            +
   stat_summary(
         fun    = "mean"
       , geom     = "point"
       , shape    =  23
       , size     =  2
       , fill     = "red"
       )                   +
   theme_bw()              +
   ggtitle("Covariate by treatment Box Plot") +
   xlab("Treatment")
print(Plot)