[R] Change the order of variables in a linear model
Frank Paetzold
Frank.Paetzold at q-das.de
Wed May 16 12:22:32 CEST 2012
Hello,
the following lines
m <- matrix(c(1,1,9,1,2,6,1,3,7,2,1,4,2,2,5,2,3,1,3,1,2,3,2,-1,3,3,-2), 9,
3, byrow = TRUE, dimnames=list(NULL, cbind('A','B','Y')))
md <- as.data.frame(m)
md$A <- as.factor(md$A)
md$B <- as.factor(md$B)
mm <- model.matrix(Y~A+B+A:B, data=md)
produce
> mm
(Intercept) A2 A3 B2 B3 A2:B2 A3:B2 A2:B3 A3:B3
1 1 0 0 0 0 0 0 0 0
2 1 0 0 1 0 0 0 0 0
3 1 0 0 0 1 0 0 0 0
4 1 1 0 0 0 0 0 0 0
5 1 1 0 1 0 1 0 0 0
6 1 1 0 0 1 0 0 1 0
7 1 0 1 0 0 0 0 0 0
8 1 0 1 1 0 0 1 0 0
9 1 0 1 0 1 0 0 0 1
attr(,"assign")
[1] 0 1 1 2 2 3 3 3 3
attr(,"contrasts")
attr(,"contrasts")$A
[1] "contr.treatment"
attr(,"contrasts")$B
[1] "contr.treatment"
However, instead of the order
(Intercept) A2 A3 B2 B3 A2:B2 A3:B2 A2:B3 A3:B3
| |
changed order
i'd like to have | |
(Intercept) A2 A3 B2 B3 A2:B2 A2:B3 A3:B2 A3:B3
that is, the order of the A:B interaction variables is changed.
Is there a way to freely position variables in a model?
Thank you,
Frank
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