Hello,
I'm trying to replicate the following analysis in SAS PROC MIXED using the SPSS MIXED command. Here is the model being fitted:
proc mixed data = ratbrain;
class animal region treatment;
model activate = region treatment region*treatment / s;
random int / subject = animal type=vc v vcorr solution;
repeated region treatment / subject=animal type=un@un r rcorr;
run;
There are six measures per animal, defined by three regions and two treatments per region.
Here is the output from fitting this model in SAS:
Covariance Parameter Estimates
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Cov Parm Subject Estimate
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Intercept animal 7637.3000
region UN(1,1) animal 2127.7400
UN(2,1) animal 1987.2900
UN(2,2) animal 2744.6600
UN(3,1) animal 1374.5100
UN(3,2) animal 2732.2200
UN(3,3) animal 3419.7000
treatment UN(1,1) animal 1.0000
UN(2,1) animal -0.4284
UN(2,2) animal 0.6740
I would like to try and fit the same model using MIXED in SPSS. However, I'm having a very hard time figuring out how to do this. Here is what I've tried:
MIXED
activate BY region treatment
/CRITERIA = CIN(95) MXITER(100) MXSTEP(5) SCORING(1)
SINGULAR(0.000000000001) HCONVERGE(0, ABSOLUTE)
LCONVERGE(0, ABSOLUTE) PCONVERGE(0.000001, ABSOLUTE)
DFMETHOD(KENWARDROGER)
/FIXED = region treatment region*treatment | SSTYPE(3)
/METHOD = REML
/PRINT = SOLUTION G
/RANDOM INTERCEPT | SUBJECT(animal) COVTYPE(UN) SOLUTION
/repeated region*treatment | subject(animal) kronecker(region treatment) covtype(un_un)
/SAVE = PRED RESID .
I get an error message saying that the region and treatment variables cannot be included in both the repeated statement and the kronecker option. I can't remove the repeated variables, and I need to use the kronecker() option if covtype is un_un. I'm at a bit of a loss as to how to fit the same model. When I create a new variable called "measure" with values 1, 2, 3, 4, 5, 6 for each animal, and use that as the repeated variable with the region and treatment variables specified as the kronecker measures, I simply get a convergence error and no output.
I'd welcome any help on how to fit this model using SPSS MIXED. Thanks in advance!
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Brady West
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#SPSSStatistics