Points
divide points into 3 equal parts:
i@part = floor(fit(rand(@ptnum+.258), 0, 1, 0, 2.9));
Nage replacement
@nage = fit(@age,0,@life,0,1);
Group from class:
string grpname = sprintf("class_%d", i@class);
setprimgroup(0, grpname, @primnum, 1); // use setpointgroup() if running over points