# Tips:Simulate generalized gamma distributed data for PROC LIFEREG

From sasCommunity

The generalized gamma distribution can be used to model gamma distributed survival times in PROC LIFEREG as well as Weibull [where Shape=1], exponential [Shape=1, Scale=1] and lognormal [Shape=0] survival times.

To simulate a data set that will generate results in PROC LIFEREG with specific values for the shape, scale, intercept and other parameters, the following code can be used:

a=1/(Shape**2); c=Scale/Shape; b=exp(xb)/(a**c); r=rangam(0,a); X=b*(r**c);

where **X** is the generated survival time and **xb** can be the intercept, for intercept-only models, or a linear combination of covariates, such as:

xb = intercept + beta1*x1 + beta2*x2;

where **x1** and **x2** are covariates and **beta1** and **beta2** are the corresponding parameter estimates.