Hi there,
I just got below code, does anyone can help explain a little bit on the matrix following lsmestimate statement.
What does the matrix stands for?
From statistical perspective, how to explain the matrix? Thanks!
you could simply set time has 4 values like 1 ,2, 3, 4
trt has 2 values as 'A' 'B'
subgroup has 3 values as 'High' 'Low' 'Mid'
proc mixed data = test method = reml order = internal cl covtest;
class id time trt (ref = 'A') subgroup ;
model CHANGE = BASE*time trt*time*subgroup / solution ddfm=KR singular=1e-10;
repeated time / type=un subject=id;
lsmeans trt*time*subgroup / pdiff om cl alpha=0.05;
lsmestimate trt*time*subgroup
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
-2 1 1 2 -1 -1,
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
1 -2 1 -1 2 -1,
0 0 0 0 0 0
0 0 0 0 0 0
0 0 0 0 0 0
1 1 -2 -1 -1 2 /divisor=3 joint elsm cl e alpha=0.05;
run;
The documentation for the LSMESTIMATE statement explains the meaning of the values.
I suggest you start by understanding the ideas for a single categorical variable, then try to understand a two-way interaction.
Your example shows a three-way interaction. There are three separate estimates specified. Each estimate involves 24 (=4*2*3) coefficients. The three estimates are separated by commas.
In addition to the doc, I recommend "CONTRAST and ESTIMATE Statements Made Easy: The LSMESTIMATE Statement"
by Kiernan, Tobias, Gibbs, and Tao (2001)
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