[R] MANOVA

[Jorge Magalhaes]

I tried to compute Wilks Lamdba with the following code.

cccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

> metA<-read.table('./methodA.txt', header=T)
> metB<-read.table('./methodB.txt', header=T)
> metAbar<-apply(metA,2,mean)
> metBbar<-apply(metB,2,mean)
> metAcentred<-t(t(metA)-metAbar) # column centred Xij-xibar
> metBcentred<-t(t(metB)-metBbar) # column centred 
> WA<-crossprod(metAcentred) # compute W matrix 
> WB<-crossprod(metBcentred) # compute W matrix 
> Wt <- WA + WB
> met <- rbind(metA, metB) # all data in the same matrix
> metbar<-apply(met, 2, mean) # global mean vector
> BA <- nrow(metA) * (metAbar - metbar) %*% (t(metAbar)-t(metbar)) # compute B matrix  
> BB <- nrow(metB) * (metBbar - metbar) %*% (t(metBbar)-t(metbar)) # compute B matrix 
> Bt <- BA + BB
> lamdba <- det(Wt) / det(Bt+Wt) # Wilks Lamdba
> lamdba
[1] 0.4541112
> Wt.Bt.prod <- t(Wt) %*% Bt
> pillar <- eigen(Wt.Bt.prod)  # eigen for the Pillai test

ccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccccc

Somebody can comment this code?

Jorge


...........................................
The data:
 
"Method A (Sludge calcinated at 1100 C)"

methodA.txt
............................................
 Chromium	Nickel	Aluminum	Zinc
 2.0	3.0	2.7	2.3
 2.1	3.1	2.8	2.2
 1.9	3.2	2.6	2.3
 2.2	3.1	2.8	2.2
 ..........................................

"Method B (Sludge calcinated at 1500 C)"

methodB.txt
............................................  
 Chromium	Nickel	Aluminum	Zinc
 2.1	3.1	2.6	2.2
 2.3	2.9	3.0	2.5
 1.9	3.0	2.6	2.2
 2.2	3.0	2.9	2.1
 2.4	3.1	2.7	2.2
 2.3	3.0	2.6	2.1
 1.8	2.8	2.7	2.0
 ...........................................

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