The MDS Procedure

Comparison with Earlier Procedures

PROC MDS shares many of the features of the ALSCAL procedure (Young, Lewyckyj, and Takane 1986; Young 1982), as well as some features of the MLSCALE procedure (Ramsay 1986). Both PROC ALSCAL and PROC MLSCALE are no longer a part of SAS; however, they are described in the SUGI Supplemental Library User’s Guide, Version 5 Edition. The MDS procedure generally produces results similar to those from the ALSCAL procedure (Young, Lewyckyj, and Takane 1986; Young 1982) if you use the following options in PROC MDS:

  • FIT=SQUARED

  • FORMULA=1 except for unfolding data, which require FORMULA=2

  • PFINAL to get output similar to that from PROC ALSCAL

Running the MDS procedure with certain options generally produces results similar to those from using the MLSCALE procedure (Ramsay 1986) with other options. This is illustrated with the following statements: 

proc mds fit=log level=loginterval ... ;

proc mlscale stvarnce=constant suvarnce=constant ... ;

Alternatively, using the FIT=DISTANCE option in the PROC MDS statement produces results similar to those from specifying the NORMAL option in the PROC MLSCALE statement.