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Example 7.7 from Generalized Linear Mixed Models: Modern Concepts, Methods and Applications by Walter W. Stroup (p-235)

Source: R/Exam7.7.R
Exam7.7.Rd

Exam7.7 is an explaination of segmented regression

References

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

See also

DataSet7.7

Author

  1. Muhammad Yaseen (myaseen208@gmail.com)

  2. Adeela Munawar (adeela.uaf@gmail.com)

Examples


library(splines)
library(ggplot2)

DataSet7.7$a  <- factor(x = DataSet7.7$a)
knots <- c(0, 0, 0, 0, 10, 10, 20, 30, 40, 40, 40, 45, 45, 45, 50, 50, 50)

bx <- splineDesign(knots = knots, x = DataSet7.7$x, outer.ok = TRUE)

Exam7.7fm <- lm(formula = y ~ a*bx, data  = DataSet7.7)
anova(Exam7.7fm)
#> Analysis of Variance Table
#> 
#> Response: y
#>            Df Sum Sq Mean Sq  F value Pr(>F)    
#> a           1      7     6.8   0.4041 0.5255    
#> bx         10  67794  6779.4 405.7268 <2e-16 ***
#> a:bx       10   4419   441.9  26.4455 <2e-16 ***
#> Residuals 248   4144    16.7                    
#> ---
#> Signif. codes:  0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1

Data  <- data.frame(DataSet7.7, fit = Exam7.7fm$fit)
##---Estimated response surface by using segmented regression
Plot <-
     ggplot(data = Data , mapping = aes(x = x, y = y, colour = a)) +
     geom_point() +
     geom_line(linewidth = 1) +
     ggtitle("Response surface by using segmented regression")

print(Plot)