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| The SURVEYLOGISTIC Procedure |
| CLASS Statement |
The CLASS statement names the classification variables to be used in the analysis. The CLASS statement must precede the MODEL statement. You can specify various v-options for each variable by enclosing them in parentheses after the variable name. You can also specify global v-options for the CLASS statement by placing them after a slash (/). Global v-options are applied to all the variables specified in the CLASS statement. However, individual CLASS variable v-options override the global v-options.
- CPREFIX= n
specifies that, at most, the first n characters of a CLASS variable name be used in creating names for the corresponding dummy variables. The default is
, where 
is the formatted length of the CLASS variable. - DESCENDING
- DESC
- LPREFIX= n
specifies that, at most, the first n characters of a CLASS variable label be used in creating labels for the corresponding dummy variables.
- ORDER=DATA | FORMATTED | FREQ | INTERNAL
specifies the sorting 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 might be useful when you use the CONTRAST statement. 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.
The following table shows how PROC SURVEYLOGISTIC interprets values of the 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
By default, ORDER=FORMATTED. For FORMATTED and INTERNAL, the sort order is machine dependent.
For more information about sorting 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. Design matrix columns are created from CLASS variables according to the following coding schemes; the default is PARAM=EFFECT.
- EFFECT
specifies effect coding
- GLM
specifies less-than-full-rank, reference cell coding; this option can be used only as a global option
- ORDINAL
specifies the cumulative parameterization for an ordinal CLASS variable
- POLYNOMIAL | POLY
specifies polynomial coding
- REFERENCE | REF
specifies reference cell coding
- ORTHEFFECT
orthogonalizes PARAM=EFFECT
- ORTHORDINAL | ORTHOTHERM
orthogonalizes PARAM=ORDINAL
- ORTHPOLY
orthogonalizes PARAM=POLYNOMIAL
- ORTHREF
orthogonalizes PARAM=REFERENCE
If PARAM=ORTHPOLY or PARAM=POLY, and the CLASS levels are numeric, then the ORDER= option in the CLASS statement is ignored, and the internal, unformatted values are used.
EFFECT, POLYNOMIAL, REFERENCE, ORDINAL, and their orthogonal parameterizations are full rank. The REF= option in the CLASS statement determines the reference level for EFFECT, REFERENCE, and their orthogonal parameterizations.
Parameter names for a CLASS predictor variable are constructed by concatenating the CLASS variable name with the CLASS levels. However, for the POLYNOMIAL and orthogonal parameterizations, parameter names are formed by concatenating the CLASS variable name and keywords that reflect the parameterization.
- REF=’level’ | keyword
specifies the reference level for PARAM=EFFECT or PARAM=REFERENCE. For an individual (but not a global) variable REF= option, you can specify the level of the variable to use as the reference level. 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.
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Copyright © 2009 by SAS Institute Inc., Cary, NC, USA. All rights reserved.