I have three datasets, each containing the values of a variable for a different 6-month period, and I'm trying to use their values as the time-dependent explanatory variable, in a proportional hazards model (PROC PHREG). Basically, from time 1 to time 6, I want the value of the explanatory variable to be the value from table 1; from time 7 to 12 I want the value of the same explanatory variable to be the value from table 2, etc. I know I will have to join all the datasets before I run PHREG, but my question is how do I flag them prior to that, to allow me to differentiate the values coming from each dataset? (EDIT) To clarify what I mean: Dataset 1 contains the values of variable "Measurement" for the period Jan 2010 - Jun 2010 Dataset 2 contains the values of variable "Measurement" for the period Jul 2011 - Dec 2011 Dataset 3 contains the values of variable "Measurement" for the period Jan 2011 - Jun 2011 I want to combine the values of "Measurement" from all 3 datasets into one single model for PHREG, that selects the value from Dataset 1 during time 1 to time 6, the value from Dataset 2 from time 7 to time 12, and the value from Dataset 3 from time 13 to time 18. What would be a good and clean way to do this? Greatly appreciate any help.
... View more