Number of observation by expression.

[TimurShangareev]

I want to get observation number from expression <dsname(where=(...))> by using macro code. So I could write in any place (inside other procedure or %if statement) %if %sysfunc(nobs(dsname(where=(...)))) > 0 %then %do;  BY-statement-code; %end;

My current solution uses PROC FCMP and DOSUBL inside custom function NOBS. After all I use %sysfunc(NOBS(...)). Inside NOBS function I use NOBS ATTRN to obtain answer if possible. Otherwise, inside DOSUBL I use PROC SQL to count observation number. Is there any other universal solution, which more stable than NLOBSF?

I think I could use FETCH inside NOBS function, but I don't know: should I extract WHERE= option and then apply something like If not where_string then delete; But there is a problem, that i can't in one function call extract where_string and use it as code. 

DOSUBL seems very hard for performance. It's intitializes additional environment/space/memory?

Is there a way to do this elegantly and reliably?

[Quentin]

What is your concern with using NLOBSF?

Years ago I was inspired by this paper by Jack Hamilton:

https://support.sas.com/resources/papers/proceedings/proceedings/sugi26/p095-26.pdf

And wrote a obscount macro, the core of which is to use NLOBS if SAS knows the number of records and there is no WHERE options, else use NLOBSF:

    %if %sysfunc(attrn(&idnum, ANOBS)) and %sysfunc(attrn(&idnum, WHSTMT))=0 %then %do;
      %*If sas knows number of obs, and there is no where statement, get nlobs;
      %let nlobs = %sysfunc(attrn(&idnum,nlobs)); %*get number of obs;
    %end;
    %else %if %sysfunc(attrn(&idnum, ANOBS))=0 
              or (1<=%sysfunc(attrn(&idnum, WHSTMT)) and %sysfunc(attrn(&idnum, WHSTMT)) <=3) %then %do;
      %*If sas doesnt know number of obs, or there is a where statement, get nlobsf (this iterates through dataset);
      %let nlobs = %sysfunc(attrn(&idnum,nlobsf)); %*get number of obs;
    %end; 

Yes, DOSUBL is slow compared to most other functions, because it's doing a LOT of work (creating and destroying the side session to run execute the code). 

[Tom]

Why not use FETCH ?  Been using it for a LOOONG time.

https://github.com/sasutils/macros/blob/master/nobs.sas