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st: create one factor level from two existing

From   "Lane, Scott D" <>
To   "" <>
Subject   st: create one factor level from two existing
Date   Wed, 26 Dec 2012 11:37:17 -0600

I have a design with 2 placebo (plc) doses (a baseline plc, designated 1, to familiarize/stabilize subjects on a lab task) plus three CNS-active doses and an additional plc dose (designated 2-5 and counterbalanced).  Performance on the 2 placebo doses is highly correlated and I thus wish the combine the 2 placebos into 1 plc factor in the analytic model (e.g., dose with 4 levels).  In the .dat file, the data are in long format with several other DVs and IVs for each subject.  Please advise re: how to use egen (or some other technique) to pull this off?  To date, I have tried:
1. egen rowmeans for each of the 2 plc doses, then attempted, by subject, to average the 2 newly created variables (result = a variable of blank values).
2. reshape to wide format, then use egen rowmeans (result = error message stating that most of the other IVs and DVs cannot be reshaped to wide format).  Thus, I cannot get started without deleting many other variables.

Any suggestions would be most welcome.
SD Lane
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