Time: number of days from between the scans (follow-up). for subject 2 first scan at time 0, second scan at after 20 days from the previous scan, 3rd scan after 25 days from the previous scan and 4th scan again after 25 days from the previous scan. similarly for other patients. for 4th subject: first scan at time 0, second scan at after 50 days from the previous scan, 3rd scan after 28 days from the previous scan, 4th scan again after 20 days from the previous scan, 5th scan after 50 days from the previous scan and last 6th scan after 28 days from the previous scan. data test; input followup volume time; datalines; 1 1 0 2 5 10 1 1 0 2 7 20 3 10 25 4 11 25 1 1 0 2 9 30 3 12 15 4 19 30 1 1 0 2 10 50 3 11 28 4 12 20 5 15 50 6 25 28 ; run; Re: Proc NLIN! Is it helpful?
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