The REPLICATE statement provides a way to accommodate models in which different subjects have identical data. This occurs most commonly when the dependent variable is binary. When you specify a REPLICATE variable, PROC NLMIXED assumes that its value indicates the number of subjects having data identical to those for the current value of the SUBJECT= variable (specified in the RANDOM statement). Only the last observation of the REPLICATE variable for each subject is used, and the replicate variable must have only positive integer values.

Note that the REPLICATE mechanism is different from using a FREQ statement in other statistical modeling procedures, such as PROC GLM, GENMOD, GLIMMIX, and LOGISTIC. A FREQ variable is used to identify grouped values for observations, essentially multiplying the log likelihood or sum of squares contribution for the observation. A REPLICATE variable is used to multiply the contribution of a subject that comprises one or more observations.