/*-------------------<-- Start of Description -->--------------------\
| Generate random variate from a normal distribution |
|-----------------------------------------|
|--------------------------------------------------------------------|
|-------------------------|
| Arguments Need: |
| seed - seed; Required, default is the current system time; |
| var - the variable to save the generated random variates; |
| alpha - alpha; |
| beta - beta; |
| Note: mean=a/(a+b), variance=a*b/(a+b)^2*(a+b+1); |
| temp - the temporary variable to update the seed; |
| default is _rannor0_; |
|---------------------------|
|--------------------------------------------------------------------|
|---------------------------------|
|Example |
| data one; |
| do i=1 to 20; |
| x=%_ranbeta(seed=1, alpha=2, beta=2); |
| %_ranbeta(var=y, seed=12, alpha=2, beta=2); |
| output; |
| end; |
| run; %print(one); |
|Usage: %_ranbeta(seed=%sysfunc(datetime(), 15.), alpha=REQUIRED, |
| beta=REQUIRED, var=, temp=_ranbeta0_); |
\----------------------------------*/
%macro _ranbeta(seed=%sysfunc(datetime(), 15.), alpha=REQUIRED,
beta=REQUIRED, var=);
/*--------------------------------------------\
| Copy Right: Duo Zhou; |
| Created: 3-22-2002 6:30pm; |
| Purpose: Random Beta Generator; |
\--------------------------------------------*/
%local nseed seed1 seed2;
%let _achk_=%sysfunc(rxmatch(%sysfunc(rxparse($a|$A|$w)),&alpha));
%let _bchk_=%sysfunc(rxmatch(%sysfunc(rxparse($a|$A|$w)),&beta));
%if (%quote(&seed) eq) or &_achk_ or &_bchk_ %then %do;
%if (%quote(&seed) eq) %then %do;
%put ==> Error: This is not a valid seed!;
%if (%length(&var)) %then %do; &var=.; %end;
%else %do; .;%end;
%end;
%if &_achk_ %then %do;
%put ==> Error: &alpha is not a valid alpha!;
%if (%length(&var)) %then %do; &var=.; %end;
%else %do; .;%end;
%end;
%if &_bchk_ %then %do;
%put ==> Error: &beta is not a valid beta!;
%if (%length(&var)) %then %do; &var=.; %end;
%else %do; .;%end;
%end;
%goto finish;
%end;
%else %do;
%let nseed=1; %let seed1=%qscan(&seed, &nseed, %str( ()));
%do %while(%length(&&seed&nseed));
%put seed&nseed is &&seed&nseed;
%let nseed=%eval(&nseed+1);
%let seed&nseed=%qscan(&seed, &nseed, %str( ()));
%end;
%let nseed=%eval(&nseed-1);
%if (&nseed<2) and (not %sysfunc(rxmatch(%sysfunc(rxparse(.|_|$a|$A|$w)),&seed))) %then %do;
%if %length(&seed) ge 2 %then %do;
%let seed1=%substr(&seed, 1, %eval(%length(&seed)/2));
%let seed2=%substr(&seed, %eval(%eval(%length(&seed)/2)+1), %eval(%length(&seed)-%eval(%length(&seed)/2)));
%end;
%else %do;
%let seed1=&seed; %let seed2=&seed;
%end;
%end;
%else %if (&nseed>=2) %then;
%else %do;
%let seed1=substr(&seed, 1, floor(length(&seed)/2));
%let seed2=substr(&seed, (floor(length(&seed)/2)+1), (length(&seed)-(floor(length(&seed)/2))));
%end;
%if (%length(&var)) %then %do;
drop _tmp_&var;
%_rangam(seed=&seed1, alpha=&alpha, var=&var);
%_rangam(seed=&seed2, alpha=&beta, var=_tmp_&var);
&var=&var/(&var+_tmp_&var);
%end;
%else 1/(1+%_rangam(seed=&seed1, alpha=&beta)/%_rangam(seed=&seed2, alpha=&alpha));
%end;
%finish:
%mend _ranbeta;