turn on suggestions

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

Showing results for

Find a Community

- Home
- /
- Analytics
- /
- Stat Procs
- /
- Is it possible to specify 3 repeated factors in Pr...

Topic Options

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

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

05-30-2014 03:09 PM

I'm trying to specify three repeated factors in Proc Mixed. I'm able to specify one or two repeated factors depending on the covariance structure specified in the Repeated statement. (Two repeated factors seems to require Type=un@cs or Type=un@un.) However, I've had no success with three repeated factors. Is it a matter of specifying the appropriate covariance structure, or does Proc Mixed not handle more than 2 repeated factors?

Below is the code I'm running. The data is stacked as it should be.

proc mixed data=subject5;

class subject pricea priceb pricec;

model rate=pricea|priceb|pricec/ddfm=kr;

repeated pricea priceb pricec/subject=subject type=un@un;

run;

Thanks for any help anyone can provide.

Accepted Solutions

Solution

05-31-2014
10:32 PM

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

Posted in reply to DannyWeathers

05-31-2014 10:32 PM

I would consider writing the following REPEATED statement:

repeated pricea*priceb*pricec / subject=subject type=un;

Ryan

All Replies

Solution

05-31-2014
10:32 PM

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

Posted in reply to DannyWeathers

05-31-2014 10:32 PM

I would consider writing the following REPEATED statement:

repeated pricea*priceb*pricec / subject=subject type=un;

Ryan

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

Posted in reply to Ryan

06-02-2014 08:54 AM

This is undoubtedly the only way to get after this, unless there is a natural nesting of some of the factors. I would be curious about the design that gives rise to this--would it be possible to reparameterize so that this could be fit in a less "bulky" form. I worry about the following--suppose each of the prices has three levels. The three-way interaction will have 27 levels, and an unstructured matrix will require estimating 351 parameters. It is going to take a large dataset to get good estimates for that many parameters.

Steve Denham

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

Posted in reply to SteveDenham

06-02-2014 11:02 AM

Steve, You guessed right. Each price did have 3 levels. Each subject evaluated 27 product "bundles." Each bundle contained the same 3 products, and the prices of each product were manipulated at 3 levels each. Subjects rated the attractiveness of the overall bundle. I'll consider ways to reparameterize the model, but our goal is to test for possible interactions between the prices.

Thanks for your help.

Danny

- Mark as New
- Bookmark
- Subscribe
- Subscribe to RSS Feed
- Permalink
- Email to a Friend
- Report Inappropriate Content

Posted in reply to DannyWeathers

06-02-2014 11:14 AM

Ryan's suggestion should work, but you will need about 10 times as many records as parameters to be able to get it to converge to anything reasonable.

(And a fairly intense computing platform).

Steve Denham