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11-22-2011 05:51 AM

Dear all

I'm using proc mixed for repeated mesaures with the code below:

Proc mixed data=ds_input;

class id m_time;

model y=x1 x2 x3 /solution;

repeated m_time / type=un subject=id;

run;

Could anyone explain me the difference between the sintax type=un and type=un(1)? What's the meaning of Banded Covariance structure?

When is it recommend to use a banded covariance structure? and an autoregressive covariance structure?

Thanks in advance for any help

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Solution

11-22-2011
08:45 AM

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11-22-2011 08:45 AM

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Solution

11-22-2011
08:45 AM

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11-22-2011 08:45 AM

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08-06-2013 03:34 PM

Dear lvm, what is the difference between UN(1) and CSH then ? Thank you.

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Posted in reply to stan

08-06-2013 03:43 PM

Big difference. With UN(1), all the covariances (and thus correlations) within subjects are 0. The variances are all different (potentially) for each group. With CSH, there is also a separate variance for each group, but there are nonzero covariances for the pairs of times. With CSH, there is a single correlation for all possible pairs, but because the variances can be different, the covariances will also be different. The User's Guide for MIXED has a nice table showing the covariance matrix for many of the different structures.