Turn on suggestions

Auto-suggest helps you quickly narrow down your search results by suggesting possible matches as you type.

Showing results for

- Home
- /
- Analytics
- /
- Stat Procs
- /
- prox mixed Example 79.5 Random Coefficients

Options

- RSS Feed
- Mark Topic as New
- Mark Topic as Read
- Float this Topic for Current User
- Bookmark
- Subscribe
- Mute
- Printer Friendly Page

🔒 This topic is **solved** and **locked**.
Need further help from the community? Please
sign in and ask a **new** question.

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Posted 09-08-2018 05:16 PM
(1479 views)

Hello all

I am new to PROC MIXED and having a trouble understanding SAS Doc Example (Example 79.5 Random Coefficients) as referenced here. So in the first part of the example, we fit the following random intercept/slope model to the RC data with 'Batch' as the grouping (clustering) element:

proc mixed data=rc; class Batch; model Y = Month / s; random Int Month / type=un sub=Batch s; run;

And based on Output 79.5.3, we have 2 columns per each subject which translates to 6 random effects that are related to each other with a full unstructured format. This means that the G matrix is 6 by 6 and all of 36 elements are parameters to be estimated. But later on, when I look at Output 79.5.5, I can only find 4 of those estimates. So the question is what happened to other G parameter estimates and how I can retrieve those?

Appreciate any words of wisdom anyone could share.

- Tags:
- proc mixed

1 ACCEPTED SOLUTION

Accepted Solutions

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

`Int`

and `Month," `

which includes the sentence, "In mixed model notation, G is block diagonal with unstructured 2x2 blocks. "

4 REPLIES 4

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

`Int`

and `Month," `

which includes the sentence, "In mixed model notation, G is block diagonal with unstructured 2x2 blocks. "

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Thanks much, it indeed helps out.

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

Is there any way to extract the full G matrix when we specify SUBJECT= option?

In reading the document as referenced here, it mentions "*If you specify the SUBJECT= option, then the block of the matrix corresponding to the first subject is displayed*".

However I'd like to see the full G matrix for all blocks (even though if they might be identical which in this example because of TYPE=UN, I think that's not the case). A use case I am following is to fully reproduce "Solution for Random Effects" estimates (gamma hat) as defined by

Thanks again

- Mark as New
- Bookmark
- Subscribe
- Mute
- RSS Feed
- Permalink
- Report Inappropriate Content

The "full matrix" is block-diagonal. You can use the BLOCK function in SAS/IML (a matrix language) to construct block-diagonal matrices. An example is shown in the article "Constructing block matrices with applications to mixed models."

You can also use the MMEQ and MMEQSOL options to get the matrix expression for the mixed model equations. (Not sure if this last solution is relevant to your case.)

**Don't miss out on SAS Innovate - Register now for the FREE Livestream!**

Can't make it to Vegas? No problem! Watch our general sessions LIVE or on-demand starting April 17th. Hear from SAS execs, best-selling author Adam Grant, Hot Ones host Sean Evans, top tech journalist Kara Swisher, AI expert Cassie Kozyrkov, and the mind-blowing dance crew iLuminate! Plus, get access to over 20 breakout sessions.

What is ANOVA?

ANOVA, or Analysis Of Variance, is used to compare the averages or means of two or more populations to better understand how they differ. Watch this tutorial for more.

Find more tutorials on the SAS Users YouTube channel.