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Call Execute in the Data Step
- This article needs a better introduction and additional explanation of the concepts being demonstrated. See the discussion page for more information.
let's start off with a simple macro that spits out some text and the value of a variable:
%macro ex(text,var); %put &text &var; %mend;
now let's try to execute the macro twice, once in a call execute statement ('in call' at line 353) and then in a regular stand-alone version ('regular' at line 354):
351 data _null_; 352 x = 3; 353 call execute('%ex(in call,'|| x || ')'); 354 %ex(regular, x); regular x 355 run; NOTE: Numeric values have been converted to character values at the places given by: (Line):(Column). 353:33 in call 3 NOTE: DATA statement used (Total process time): real time 0.00 seconds user cpu time 0.00 seconds system cpu time 0.00 seconds Memory 135k NOTE: CALL EXECUTE routine executed successfully, but no SAS statements were generated.
notice the placement of the two different macro executions? the call execute macro statement was executed after the data step finished while the regular macro statement was executed when the data step was being compiled. interesting, don't you think?
it gets better. let's look at how these two beasts behave in a loop:
356 data _null_; 357 do x = 1 to 3; 358 call execute('%ex(in call,'|| x || ')'); 359 %ex(regular, x); regular x 360 end; 361 run; NOTE: Numeric values have been converted to character values at the places given by: (Line):(Column). 358:35 in call 1 in call 2 in call 3 NOTE: DATA statement used (Total process time): real time 0.01 seconds user cpu time 0.00 seconds system cpu time 0.00 seconds Memory 135k NOTE: CALL EXECUTE routine executed successfully, but no SAS statements were generated.
now it seems that the regular macro statement executes in place, but because it is executed during DATA step compilation (before the loop is executed), it only executes once even though it is inside a loop. the call execute macro statement executes post-data step three times as expected.
the call execute documentation explains:
- If an EXECUTE routine argument is a macro invocation or resolves to one, the macro executes immediately. However, any SAS statements produced by the EXECUTE routine do not execute until after the step boundary has been passed.
if you're not expecting it, this behavior can definitely throw you for a loop.
--RichardK 14:06, 16 January 2008 (EST)
The macro generates a %PUT statement, which is global. The %PUT statement spawned in the "regular" fashion is processed during the compilation of the DATA step; it does not become part of the executable DATA step.--Howles 22:49, 5 October 2008 (EDT)