CLASS variables </ options> ;
The CLASS statement names the classification variables to be used in the analysis. Typical class variables are Treatment, Sex, Race, Group, and Replication. If the CLASS statement is used, it must appear before the MODEL statement.
Classification variables can be either character or numeric. Class levels are determined from the formatted values of the
variables. Thus, you can use formats to group values into levels. See the discussion of the FORMAT procedure in the
Base SAS Procedures Guide and the discussions of the FORMAT statement and SAS formats in
SAS Formats and Informats: Reference.
You can specify the following options for classification variables:
-
DESCENDING
DESC
-
reverses the sort order of the classification variable. If you specify both the DESCENDING and ORDER= options, PROC ADAPTIVEREG
orders the categories according to the ORDER= option and then reverses that order.
-
ORDER=order-type
-
specifies the sort order for the categories of categorical variables. This ordering determines which parameters in the model
correspond to each level in the data. 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. Table 24.2 shows how PROC ADAPTIVEREG interprets values of the ORDER= option.
Table 24.2: Sort Order for Categorical Variables
|
order-type
|
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
|
|
FREQDATA
|
Order of descending frequency count, and within counts by order of appearance in the input data set when counts are tied
|
|
FREQFORMATTED
|
Order of descending frequency count, and within counts by formatted value (as above) when counts are tied
|
|
FREQINTERNAL
|
Order of descending frequency count, and within counts by unformatted value when counts are tied
|
|
INTERNAL
|
Unformatted value
|
For the FORMATTED and INTERNAL values, the sort order is machine-dependent. If you specify the ORDER= option in the MODEL
statement and the ORDER= option in the CLASS statement, the former takes precedence.
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.
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