modeling the circadian baseline

Dear NM users, A biomarker, which shows clear circadian rhythm during placebo treatment, was described by a turnover model with the introduction of a periodic time-dependent production function KST with two harmonics. The code in $DES is written as follows: $DES DPI = 3.14159 DPS1 = KOUT*A0 DPS2 = (KOUT*A1 + B1*DPI/12)*DCOS(DPI*T/12) DPS3 = (KOUT*B1 - A1*DPI/12)*DSIN(DPI*T/12) DPS4 = (KOUT*A2 + B2*DPI/6) *DCOS(DPI*T/6) DPS5 = (KOUT*B2 - A2*DPI/6) *DSIN(DPI*T/6) KST = DPS1 + DPS2 + DPS3 + DPS4 + DPS5 DADT(1) = KST - KOUT*A(1) In the paper published by Hempel et al (CPT, 1998;64:622-35), a ETA was introduced in the time T which accounts for the differences in wake-up times between subjects (e.g. DCOS(DPI*(T+ETA)/12). Because ETA is prohibited in the $DES, how can I code the interindividual variability of time in the control stream? Any suggestion is highly appreciated! Kind Regards, Ying -- Ying HONG, PhD Department of Pharmaceutical Sciences University at Buffalo, SUNY C237 Cooke Hall, Buffalo, NY 14260 Tel: 716 645 2828 ext 275 Fax: 716 645 3693 E-mail: yhong6