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Re: st: -anova- command fails with mildly complexx model


From   jpitblado@stata.com (Jeff Pitblado, StataCorp)
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: -anova- command fails with mildly complexx model
Date   Fri, 16 Apr 2010 17:53:36 -0500

We promised more information about the bug in -anova- reported by Al Feiveson
<alan.h.feiveson@nasa.gov> that caused -anova- to misinterpret some
specifications and sometimes even to crash Stata.

Quick update
-------------

We have fixed the problem and that fix is now in testing and certification.
We expect to have it out as an update in the middle of next week.


Longer update
-------------

One of Al's problem commands was,

    . anova y treat group treat#group / isub|treat#group     
              time time#(group##treat)

The crash is triggered only when parentheses are used to bind terms in a
factor varlist and when interactions or subsets of interactions among the
bound terms also appear elsewhere in the specification, such as Al's
-treat#group ... time#(group##treat)-.

The bug is not limited to -anova-, it can occur in any command that accepts
factor variables.

While waiting for the update next week, Al can run his model by explicitly
specifying his terms, rather than relying on parentheses expansion. If instead
of typing,

    . anova y treat group treat#group / isub|treat#group     
              time time#(group##treat)

Al types,

     . anova y treat group treat#group / isub|treat#group     
               time time#group time#treat time#group#treat

his model will estimate correctly.


 -- Jeff Pitblado         -- Ken Higbee          -- Vince Wiggins
    jpitblado@stata.com      khigbee@stata.com      vwiggins@stata.com

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