SAS Nadir Value

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

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;