Control groups

[DLettoof]

I am assessing DRC for several metals in wild animal tissues. Some of these metals don't have a concentration of 0 (e.g., 16 - 20 mg/kg, ranging to 100s of mg/kg). I notice when I assign the lowest concentration as the control group, the plots assign it a 0 concentration. I think this is interfering with the curves and BMD calculations as it can be a big jump to the next value (e.g., 17 mg/kg).

Is there a way to run the models starting at the control group assigned values? This is especially useful for trace elements that will rarely have a 0 value....