Exam7.2: Example 7.2 from Generalized Linear Mixed Models: Modern...

In StroupGLMM: R Codes and Datasets for Generalized Linear Mixed Models: Modern Concepts, Methods and Applications by Walter W. Stroup

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(s)

1. Muhammad Yaseen ([e-mail])

2. Adeela Munawar ([e-mail])

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)

StroupGLMM documentation built on Oct. 2, 2024, 1:07 a.m.