Programming the statistical procedures from SAS

proc mixed code errors

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proc mixed code errors

Portion of the following editor is producing the classic error statement:

NOTE: An infinite likelihood is assumed in iteration 0 because of a nonpositive residual

      variance estimate

Note the data below is just a sample of it - is fully factoral with all 1-4 repeated time samples present

Data atracomp;

    Input strain $ comp $ time diam;

Datalines;

95        Fus    1    1.825772287

95        Fus    2    1.42601572

95        Fus    3    1.420739244

95        Fus    4    1.456064902

95        Lep    1    1.859838703

Fus  

Fus   1580    3    1.549731159
Fus   1580    4    1.422556384
Fus   1645    1    1.414225347
Fus   1645    2    1.589653421
Fus   1645    3    1.530931089
Fus   1645    4    1.459880132
Lep   95   1    1.654991843
Lep   95   2    1.466500938
Lep   95   3    1.421560176
Lep   95   4    1.487391453
Lep   1210    1    1.414225347
Lep   1210    2    1.657105307
Lep   1210    3    1.476058942
Lep   1210    4    1.443722042
Lep   1580    1    1.749761889
Lep   1580    2    1.448447445
Lep   1580    3    1.479019946
Lep   1580    4    1.602472049
Lep   1645    1    1.414225347
Lep   1645    2    1.598117643
Lep   1645    3    1.433091065
Lep   1645    4    1.487279395

;

proc mixed data = atracomp;

    class strain comp time;

    model diam= strain|comp|time;

    repeated time / subject=strain*comp type = cs r rcorr;

    lsmeans comp*strain/slice=comp slice=strain pdiff adj=tukey;

run;

/*same stats but running with un error structure to compare AIC*/

proc mixed data = atracomp;

    class strain comp time;

    model diam= strain|comp|time;

    repeated time*comp / subject=strain*comp type = ar(1) r rcorr;

    lsmeans comp*strain/slice=comp slice=strain pdiff adj=tukey;

run;

ANYONE FIND THE ISSUE IN THIS CODE?  It worked beautifully for a similar data set.

Grand Advisor
Posts: 10,034

Re: proc mixed code errors

NOTES are not ERRORS. They do tell you something about your data that you may not have been aware of that may compromise the analysis.
I would look to see if you have an extreme value diam.

Frequent Contributor
Posts: 130

Re: proc mixed code errors

Nothing obviously wrong with the code except..when you get it to run so that you are happy..can you assume equal variances across strain, comp and comp*strain? If not, another adjustment choice might be more appropriate.

Maybe this would get more helpful suggestions if you re-posted to the non-SAS-U-specific statistics discussion forum. The question is a bit too specialised for this forum I think. 

Cheers.

Damien

Community Manager
Posts: 538

Re: proc mixed code errors

I have moved this discussion over to the SAS Statistical Procedures Community. Experts there should be able to help!

Respected Advisor
Posts: 2,655

Re: proc mixed code errors

The most likely cause of this NOTE is the presence of a duplicate record someplace in the data.  The example data above got munged during cutting and pasting, so I can't tell if that is the problem.  The second most likely cause is an overparameterized model.  Try attaching a file in good shape regarding the data (it would be nice to have the one that works, and the one that throws the NOTE, for comparison), and maybe we can track this down.

Steve Denham

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