SPSS® 12.0 Command Syntax Reference

824 LOGLINEAR
[BASIS]SPECIAL(matrix) User-defined contrast. As many elements as the number of categories
squared must be specified. If BASIS is specified before SPECIAL,
a basis matrix is generated for the special contrast, which makes the
coefficients of the contrast equal to the special matrix. Otherwise,
the matrix specified is transposed and then used as the basis matrix
to determine coefficients for the contrast matrix.
Example
LOGLINEAR A(1,4) BY B(1,4)
/CONTRAST(B)=POLYNOMIAL
/DESIGN=A A BY B(1)
/CONTRAST(B)=SIMPLE
/DESIGN=A A BY B(1).
• The first CONTRAST subcommand requests polynomial contrasts of B for the first design.
• The second CONTRAST subcommand requests the simple contrast of B, with the last category
(value 4) used as the reference category for the second DESIGN subcommand.
Example
* Multinomial logit model
LOGLINEAR PREF(1,5) BY RACE ORIGIN CAMP(1,2)
/CONTRAST(PREF)=SPECIAL(5*1, 1 1 1 1 -4, 3 -1 -1 -1 0,
0 1 1 -2 0, 0 1 -1 0 0).
• LOGLINEAR builds special contrasts among the five categories of the dependent variable
PREF, which measures preference for training camps among Army recruits. For PREF,
1=stay, 2=move to north, 3=move to south, 4=move to unnamed camp, and 5=undecided.
• The four contrasts are: (1) move or stay versus undecided, (2) stay versus move, (3)
named camp versus unnamed, and (4) northern camp versus southern. Because these contrasts
are orthogonal, SPECIAL and BASIS SPECIAL produce equivalent results.
Example
* Contrasts for a linear logit model
LOGLINEAR RESPONSE(1,2) BY YEAR(0,20)
/PRINT=DEFAULT ESTIM
/CONTRAST(YEAR)=SPECIAL(21*1, -10, -9, -8, -7, -6, -5, -4,
-3, -2, -1, 0, 1, 2, 3, 4, 5, 6, 7,
8, 9, 10, 399*1)
/DESIGN=RESPONSE RESPONSE BY YEAR(1).
• YEAR measures years of education and ranges from 0 through 20. Therefore, allowing for
the constant effect, YEAR has 20 estimable parameters associated with it.
• The SPECIAL contrast specifies the constant—that is, 21*1—and the linear effect of
YEAR—that is, –10 to 10. The other 399 1’s fill out the 21*21 matrix.