Formula for Gamma and Lognormal distributions

gilsonk — Wed, 27 Feb 2019 04:15:03 GMT

I'm trying to use parameters derived from survival curve data using LIFEREG (ie intercept and scale) to calculate extrapolated datasets using the various distributions described in Chapter 36 (the LIFEREG procedure).

I have managed the exponential and Weibull calculations. Code for exponential distribution is below.

data exp;
	DO i=0 to 60 by 1; /*5year time frame by month*/
		t=i;
		s=exp((-exp(-3.9755))*t); /*generate intercept and scale using LIFEREG, input here*/
		dist=6;
		output;
	end;
run;

The formulae provided in the SAS documentation for the Gamma and Lognormal distributions (see Supported Distributions section) include symbols that I don't know how to write into the SAS code. Is anyone able to provide the code for these 2 distributions?

I need to complete a Gompertz extrapolation also. Is that distribution supported by SAS? It doesn't seem to be included in the LIFEREG documentation but worth asking just in case.

Many thanks, Kylie

Re: Formula for Gamma and Lognormal distributions

ballardw — Thu, 28 Feb 2019 18:03:44 GMT

I think that you may want to investigate the various distribution functions such as SDF, PDF, CDF or LOG versions of those. The allow providing the distribution name and parameters to get values from the distribution.

topic Re: Formula for Gamma and Lognormal distributions in Statistical Procedures

Formula for Gamma and Lognormal distributions

Re: Formula for Gamma and Lognormal distributions