R中的乘法设计矩阵

Question

在R，

是

model.matrix(~ Treatment + Time + Treatment*Time, table_design)

相当于

model.matrix(~ Treatment*Time, table_design)

感谢。

Answer 1

是

table_design<-data.frame(
    Treatment=rep(c("A","B"), each=10),
    Time=rpois(20,20)
)
all.equal(
  model.matrix(~ Treatment + Time + Treatment*Time, table_design), 
  model.matrix(~ Treatment*Time, table_design)
)
# [1] TRUE