-
DESCENDING
DESC
-
reverses the sort order of the classification variable. If both the DESCENDING and ORDER=
options are specified, PROC SURVEYPHREG orders the categories according to the ORDER= option and then reverses that order.
-
MISSING
-
treats missing values (".", ._, .A, …, .Z for numeric variables and blanks for character variables) as valid values for the
CLASS variable.
-
ORDER=DATA | FORMATTED | FREQ | INTERNAL
-
specifies the sort order for the levels of classification 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 the CONTRAST statement. By default,
ORDER=FORMATTED. For ORDER=FORMATTED and ORDER=INTERNAL, the sort order is machine-dependent. When ORDER=FORMATTED is in effect
for numeric variables for which you have supplied no explicit format, the levels are ordered by their internal values.
The following table shows how PROC SURVEYPHREG interprets values of the ORDER= option.
Value of ORDER=
|
Levels Sorted By
|
DATA
|
Order of appearance in the input data set
|
FORMATTED
|
External formatted values, except for numeric variables with no explicit format, which are sorted by their unformatted (internal)
values
|
FREQ
|
Descending frequency count; levels with more observations come earlier in the order
|
INTERNAL
|
Unformatted value
|
For more information about sort order, see the chapter on the SORT procedure in the
Base SAS Procedures Guide and the discussion of BY-group processing in
SAS Language Reference: Concepts.
-
PARAM=keyword
-
specifies the parameterization method for the classification variable or variables. You can specify any of the keywords shown in the following table;
Design matrix columns are created from CLASS variables according to the corresponding coding schemes:
Value of PARAM=
|
Coding
|
EFFECT
|
Effect coding
|
GLM
|
Less-than-full-rank reference cell coding (this keyword can be used only in a global option)
|
ORDINAL THERMOMETER
|
Cumulative parameterization for an ordinal CLASS variable
|
POLYNOMIAL POLY
|
Polynomial coding
|
REFERENCE REF
|
Reference cell coding
|
ORTHEFFECT
|
Orthogonalizes PARAM=EFFECT coding
|
ORTHORDINAL ORTHOTHERM
|
Orthogonalizes PARAM=ORDINAL coding
|
ORTHPOLY
|
Orthogonalizes PARAM=POLYNOMIAL coding
|
ORTHREF
|
Orthogonalizes PARAM=REFERENCE coding
|
All parameterizations are full rank, except for the GLM parameterization. The REF=
option in the CLASS statement determines the reference level for EFFECT and REFERENCE coding and for their orthogonal parameterizations.
It also indirectly determines the reference level for a singular GLM parameterization through the order of levels.
If PARAM=ORTHPOLY or PARAM=POLY and the classification variable is numeric, then the ORDER=
option in the CLASS statement is ignored, and the internal unformatted values are used. See the section Other Parameterizations in Chapter 19: Shared Concepts and Topics, for further details.
-
REF=’level’ | keyword
-
specifies the reference level for PARAM=
EFFECT, PARAM=
REFERENCE, and their orthogonalizations. For PARAM=
GLM, the REF= option specifies a level of the classification variable to be put at the end of the list of levels. This level
thus corresponds to the reference level in the usual interpretation of the linear estimates with a singular parameterization.
For an individual variable REF= option (but not for a global REF= option), you can specify the level of the variable to use as the reference level. Specify the formatted value of the variable if a format is assigned. For a
global or individual variable REF= option, you can use one of the following keywords. The default is REF=LAST.
- FIRST
-
designates the first ordered level as reference.
- LAST
-
designates the last ordered level as reference.
-
TRUNCATE<=n>
-
specifies the length n of CLASS variable values to use in determining CLASS variable levels. The default is to use the full formatted length of
the CLASS variable. If you specify TRUNCATE without the length n, the first 16 characters of the formatted values are used. When formatted values are longer than 16 characters, you can use
this option to revert to the levels as determined in releases before SAS 9. The TRUNCATE option is available only as a global
option.