The HPLMIXED Procedure

REPEATED Statement

  • REPEATED repeated-effect </ options>;

The REPEATED statement specifies the bold upper R matrix in the mixed model. If no REPEATED statement is specified, bold upper R is assumed to be equal to sigma squared bold upper I. You can use the REPEATED statement only with the BLUP option. The statement is ignored when no BLUP option is specified.

The repeated-effect is required. The repeated-effect must contain only classification variables. Make sure that the levels of the repeated-effect are different for each observation within a subject; otherwise, PROC HPLMIXED constructs identical rows in bold upper R that correspond to the observations with the same level. This results in a singular bold upper R matrix and an infinite likelihood.

Table 8 summarizes important options in the REPEATED statement. All options are subsequently discussed in alphabetical order.

Table 8: Summary of Important REPEATED Statement Options

Option Description
Construction of Covariance Structure
SUBJECT= Identifies the subjects in the R-side model
TYPE= Specifies the R-side covariance structure


You can specify the following options in the REPEATED statement after a slash (/).

SUBJECT=effect
SUB=effect

identifies the subjects in your mixed model. Complete independence is assumed across subjects; therefore, the SUBJECT= option produces a block-diagonal structure in bold upper R with identical blocks. The blocks of bold upper R correspond to observations that share the same level of SUBJECT= effect. These blocks are sorted according to this effect as well.

If you want to model nonzero covariance among all of the observations in your SAS data set, specify SUBJECT=Dummy_Intercept to treat the data as if they are all from one subject. You need to create this Dummy_Intercept variable in the data set. However, be aware that in this case PROC HPLMIXED manipulates an bold upper R matrix with dimensions equal to the number of observations.

TYPE=covariance-structure

specifies the covariance structure of the bold upper R matrix. The SUBJECT= option defines the blocks of bold upper R, and the TYPE= option specifies the structure of these blocks. The default structure is VC. You can specify any of the covariance structures that are described in the TYPE= option in the RANDOM statement.

Last updated: December 09, 2022