/*-------------------<-- Start of Description -->--------------------\ | Generate random variate from a Chisq distribution | |-----------------------------------------| |--------------------------------------------------------------------| |-------------------------| | Arguments Need: | | seed - seed; Required, default is the current system time; | | var - the variable to save the generated random variates; | | df - degree of freedom; | | Note: it is also a gamma distribution with alpha=df/2 and | | beta=2; | | temp - the temporary variable to update the seed; | | default is _ranchi0_; | |---------------------------| |--------------------------------------------------------------------| |---------------------------------| |Example | | data one; | | do i=1 to 20; | | x=%_ranchi(seed=1, df=3); | | z=%_ranchi(seed=1, df=3); | | %_ranchi(seed=12345,var=y, df=3); | | output; | | end; | | run; %print(one); | |Usage: %_ranchi(seed=%sysfunc(datetime(), 15.), df=REQUIRED, var=, | | temp=_ranchi0_); | \----------------------------------*/ %macro _ranchi(seed=%sysfunc(datetime(), 15.), df=REQUIRED, var=, temp=_ranchi0_); /*--------------------------------------------\ | Author: Duo Zhou; | | Created: 3-22-2002 6:30pm; | | Purpose: Random Chisq Generator; | \--------------------------------------------*/ %let _dfchk_=%sysfunc(rxmatch(%sysfunc(rxparse($a|$A|$w)),&df)); %if (%quote(&seed) eq) or &_dfchk_ %then %do; %if (%quote(&seed) eq) %then %do; %put ==> Error: This is not a valid seed!; %if (%length(&var)) %then %do; &var=.; %end; %else %do; .;%end; %end; %if &_dfchk_ %then %do; %put ==> Error: &df is not a valid degree of freedom!; %if (%length(&var)) %then %do; &var=.; %end; %else %do; .;%end; %end; %goto finish; %end; %else %do; %if (%length(&var)) %then %do; %if (not %sysfunc(rxmatch(%sysfunc(rxparse(_|.|$a|$A|$w)),&seed))) %then %do; drop &temp; retain &temp &seed; %let seed=&temp; %end; call rangam(&seed, &df/2, &var); &var=&var*2; %end; %else 2*rangam(&seed, &df/2); %end; %finish: %mend _ranchi;