[R] Replicating SAS example in R

Pedro Mardones mardones.p at gmail.com
Sun Apr 20 06:32:31 CEST 2014


Dear R community;

I'm trying to replicate an example I found on a publication using the
following data

dat <- data.frame(F = c(1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,
2,2,2,2,2,2,2,2,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3,3), T =
c(1,1,1,1,1,1,1,1,2,2,2,
2,2,2,2,2,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2,1,1,1,1,1,1,1,1,2,2,2,2,2,2,2,2),
R =
c(1,1,1,1,2,2,2,2,3,3,3,3,4,4,4,4,5,5,5,5,6,6,6,6,7,7,7,7,8,8,8,8,9,9,9,9,
10,10,10,10,11,11,11,11,12,12,12,12), E =
c(1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,
16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,36,37,38,39,40,41,
42,43,44,45,46,47,48), HT =
c(7.3,10.3,14.8,2.9,14.9,1.8,5.1,17.7,14.1,13,19.3,
20.7,24.9,16,14.9,24.9,24.3,28.6,31.8,32.7,29.1,24.7,30.1,31.9,42.2,45.6,40.7,
34.5,38.4,46.4,38,41.7,50.7,53.2,50.1,41.4,53,37.9,50.9,51,69.5,53.8,53.8,62.1,
54.3,63,47,65.4))

F, T are two treatments
R is a row of plants nested within F & T (according to the example)
E are the plants within the rows R

The experimental unit is R but the example considers subsampling, so in
other words, the idea is to use all the data at plant-level (E) for the
analysis instead of the row-level means.

The SAS model used in the example is

PROC GLM DATA=dat;
CLASS F T R;
MODEL HT = F|T R(F T);
TEST H = F|T E=R(F T);
CONTRAST 'First vs Third in F' F -1 0 1 / E = R(F T);
MEANS F / LSD E = R(F T) CLDIFF;
RUN;

My R version looks like
options(contrasts = c("contr.SAS", "contr.poly"))
dat$F <- as.factor(dat$F)
dat$T <- as.factor(dat$T)
dat$R <- as.factor(dat$R)
m2 <- aov(HT ~ F*T + Error(R/F*T), data = dat)
summary(m2)

which gives me similar results to the SAS example. However, I haven't been
able to replicate the CONTRAST and MEANS commands

I'd appreciate any hint (maybe using lmer instead?)

Thanks in advance

************************************************************************************

SAS output attached as pdf
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