SAS/STAT 9.2 User's Guide: The MIXED Procedure (Book Excerpt)

3904 ✦ Chapter 56: The MIXED Procedure
NOPROFILE
includes the residual variance as part of the Newton-Raphson iterations. This option applies
only to models that have a residual variance parameter. By default, this parameter is profiled
out of the likelihood calculations, except when you have specified the HOLD= option in the
PARMS statement.
ORD
ORDER=DATA
displays ordinates of the relevant distribution in addition to p-values. The ordinate can be
viewed as an approximate odds ratio of hypothesis probabilities.
ORDER=FORMATTED
ORDER=FREQ
ORDER=INTERNAL
specifies the sorting order for the levels of all CLASS variables. This ordering determines
which parameters in the model correspond to each level in the data, so the ORDER= option
can be useful when you use CONTRAST or ESTIMATE statements.
The default is ORDER=FORMATTED, and its behavior has been modified for SAS 8. When
the default ORDER=FORMATTED is in effect for numeric variables for which you have supplied
no explicit format, the levels are ordered by their internal values. In releases previous to
SAS 8, numeric class levels with no explicit format were ordered by their BEST12. formatted
values. In order to revert to the previous method you can specify this format explicitly for
the CLASS variables. The change was implemented because the former default behavior for
ORDER=FORMATTED often resulted in levels not being ordered numerically and required
you to use an explicit format or ORDER=INTERNAL to get the more natural ordering.
Table 56.4 shows how PROC MIXED interprets values of the ORDER= option.
Table 56.4 Sort Order and Value of ORDER= Option
Value of ORDER= Levels Sorted By
DATA order of appearance in the input data set
FORMATTED external formatted value, except for numeric variables
with no explicit format, which are sorted by their unformatted
(internal) value
FREQ descending frequency count; levels with the most observations
come first in the order
INTERNAL unformatted value
For FORMATTED and INTERNAL, the sort order is machine dependent.
For more information about sort order, see the chapter on the SORT procedure in the SAS
Procedures Guide and the discussion of BY-group processing in SAS Language Reference:
Concepts.