Wednesday, April 5, 2017

getvartypecount() macro function

In a prior post, I made mention of the isblank() and getattr() macro functions. I was hoping to find a way to return the number of character or numeric variables in a SAS data set using the ATTRN() SAS function. Alas, the ATTRN() function does not support what I desired neither and does DICTIONARY.TABLES (except in SAS 9.2 (TS2MO) per Dictionary Tables Reference Card where the num_character and num_numeric columns existed), so I wrote my own custom macro function.

The reason I wanted this was to dynamically set the dimension of an ARRAY that can only be a numeric constant, numeric expression or a constant. This concept works because the macro is resolved prior to the data step, this is the key to assigning the array dimension without an error. This macro function will probably tied into a subsequent post utilizing this function but here is a sneak peak at what I am trying to do:

data x ;
  if 0 then set sashelp.class ; /* Prime the PDV */
  array achar[ * ] _character_ ;
  array acount[ %getvartypecount( dsn = sashelp.class, type = C ), 2 ] ;

  /* .... more code goes here */

run ;

Below is the actual source code used to create the macro. Notice that it does use the %isblank() function referenced in the hyperlink of the first paragraph.

*     Program:
*      Author: Tom Bellmer
*     Created: 26Apr2017
* SAS Version: 9.3 (TS2M2)
*     Purpose: returns number of Character or Numeric columns in a data set  
*       Usage: %let x = %getvartypecount( dsn = sashelp.class, type = C ) ;
*       Notes: Great use to declare ARRAY dimensions since they expect
*              a numeric constant, numeric expression or constant.  Macros
*              are resolved prior to data step code so this works.
%macro getvartypecount( dsn =, type = C ) ;
  %local dsid retval i type ;
  %if %isblank( &dsn. ) %then %do ;
    %put %str(E)RROR: the DSN value is missing ;
    %return ;
  %end ;
  %let retval = 0 ;
  %let type = %upcase( &type. ) ;
  %if &type. = C or &type. = N %then %do ;
    %let dsid = %sysfunc( open( &dsn. ) ) ;
    %if &dsid. %then %do ;
      %do i = 1 %to %sysfunc( attrn( &dsid., nvars ) ) ;
        %if &type. = %sysfunc( vartype( &dsid., &i. ) ) 
         %then %let retval = %eval( &retval. + 1 ) ;
      %end ;
      %let dsid = %sysfunc( close( &dsid. ) ) ;
    %end ;
    %else %put %str(E)RROR: Invalid data set name &dsn. ;
  %end ;
  %else %put %str(E)RROR: Only valid TYPE= parameters are C or N ;
%mend ;
/* EOF:  */