Analysis of GMO vs Non-GMO Corn Hybrid Persistence Using Simulated Time Dependent Covariates in SAS

Abstract

Fitting survival models utilizing time dependent covariates with the PHREG procedure in SAS involves the utilization of programming statements within the procedure that involve array processing. Based loosely on the descriptive statistics reported by Ma and Shi, I use the SAS data step loop to simulate a data set consisting of 10,000 corn hybrids including variables for genetic modification, vertical integration, and the number of close substitutes for each hybrid for each time period. This paper demonstrates the use of PROC PHREG to fit a Cox Proportional Hazards model utilizing the simulated time dependent covariates. In addition, I demonstrate the use of the %PUT statement to verify that values of the time dependent covariates are correctly utilized for each period.

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Suggested Citation

Matt Bogard. "Analysis of GMO vs Non-GMO Corn Hybrid Persistence Using Simulated Time Dependent Covariates in SAS" 2012
Available at: http://works.bepress.com/matt_bogard/19