logistic回归class语句的param选项的说明如下:
PARAM=keyword specifies the parameterization method for the classification variable or variables. You can specify any of the keywords shown in the following table; the default is PARAM=EFFECT. 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 of 
Chapter 19: Shared Concepts and Topics, for further details.