SAS day 47: Nadir value
Definition: Nadir value is the lowest value of best response prior to current assessment or the shortest SLD (sum lesion diameter) along with the tumor measurement progress.
Example:
Measurements: 28,29,27,30,35. Nadir:28,28,27,27,27
Measurements:28,28,27,27,27. Nadir:28,28,27,27,27
Note: Nadir value is changing with the time NOT a global minimum.
Challenge: How to find nadir Value?
Key Step/Functions: Retain, Min

almapapi / Pixabay
data tlnadir; /*merge tlsum tl_sum_ly;*/ set tsum; retain nadir; by subject aday; if first.subjid then nadir=.; nadir=min(sld,nadir); nolymph=sld-lymph; run;
Output:
Sample Data:
data a; input subjid $ sld aday; datalines; 001 28 1 001 29 2 001 27 3 001 30 4 001 35 5 002 28 1 002 28 2 002 27 3 002 27 4 ; run;