Chapter 19, Section 19.5

Study of Log Progesterone Concentration during Menstrual Cycle

Mixed Model Representation of Semiparametric Regression Model for Log Progesterone Concentration

data progest;

infile 'progesterone.dat';

input id group time logp;

grptime7=group*(time-7);

*************************************************************************************************;

* Use ARRAY statement in SAS to create truncated line functions for piecewise *;

* linear curve with 22 knots located consecutively from days -7 through 14 *;

*************************************************************************************************;

array bf(22) bf1 - bf22;

do j = 1 to 22;

knot = -8 + j;

bf(j) = max(0, time - knot);

end;

drop j knot;

title1 Mixed Model Representation of Semiparametric Regression Model for Log Progesterone Concentration;

title2 Study of Log Progesterone Concentration during Menstrual Cycle;

proc mixed;

class id;

model logp = time group group*time group*bf15 / solution;

random bf1-bf22 / type=toep(1) solution;

random intercept time / subject=id type=un;

run;