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The MDS Procedure

Comparison with the ALSCAL Procedure

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:

Unlike PROC ALSCAL, PROC MDS produces no plots, so you must use output data sets and PROC PLOT or PROC GPLOT.

The MDS and ALSCAL procedures may sometimes produce different results for the following reasons:

PROC MDS accepts some PROC ALSCAL options as synonyms for the preceding options, as displayed in Table 40.1.

Table 40.1: PROC MDS Options Compared to PROC ALSCAL Options
  Accepted by Related PROC MDS Option
PROC ALSCAL Option PROC MDS? or Comments
CONDITION=Yes 
CONVERGE=YesConvergence measures are
  not comparable
CUTOFF=Yes 
DATA=Yes 
DEGREE=No 
DIMENS=Yes 
DIRECTIONS=No 
HEADERYesDefault in PROC MDS
IN=Yes 
ITER=YesMAXITER=
LEVEL=YesLEVEL=NOMINAL is not
  supported
MAXDIM=mYesDIMENSION=n TO m
MINDIM=nYesDIMENSION=n TO m
MINSTRESS=YesMINCRIT=
MODEL=EUCLIDYesCOEF=IDENTITY
MODEL=INDSCALYesCOEF=DIAGONAL
MODEL=GEMSCALNo 
MODEL=ASYMSCALNo 
MODEL=ASYMINDSNo 
NEGATIVE(Yes)In PROC MDS, the NEGATIVE
  option affects slopes and powers,
  not subject weights.
NOULBYes 
OUT=YesSome differences in contents
PLOTNo 
PLOTALLNo 
PRINTNo 
READV, etc.NoUse WHERE data set option
READFIXV, etc.No 
ROWS=No 
SHAPE=SYMMETRIYesSHAPE=TRIANGLE
SHAPE=ASYMMETRYesSHAPE=SQUARE
SHAPE=RECTANGUNoUse SHAPE=TRIANGLE with
  extra missing values to
  fill out the matrix.
SIMILARYes 
TIESTORE=YesIgnored by PROC MDS
UNTIEYes 

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