SPSS Programming and Data Management, 4th Edition: A Guide for ...

13Best Practices and Efficiency TipsStatistical and charting procedures always read the data, but most transformationcommands (for example, COMPUTE, RECODE, COUNT, SELECT IF) donotrequireaseparate data pass.The default behavior of the graphical user interface, however, is to read the datafor each separate transformation so that you can see the results in the Data Editorimmediately. Consequently, every transformation command generated from the dialogboxes is followed by an EXECUTE command. So if you create command syntax bypasting from dialog boxes or copying from the log or journal, your command syntaxmay contain a large number of superfluous EXECUTE commands that can significantlyincrease the processing time for very large data files.In most cases, you can remove virtually all of the auto-generated EXECUTEcommands, which will speed up processing, particularly for large data files and jobsthatcontainmanytransformationcommands.To turn off the automatic, immediate execution of transformations and the associatedpasting of EXECUTE commands:EEEFrom the menus, choose:EditOptions...Click the Data tab.Select Calculate values before used.Lag FunctionsOne notable exception to the above rule is transformation commands that contain lagfunctions. In a series of transformation commands without any intervening EXECUTEcommands or other commands that read the data, lag functions are calculated afterall other transformations, regardless of command order. While this might not be aconsideration most of the time, it requires special consideration in the following cases:• The lag variable is also used in any of the other transformation commands.• One of the transformations selects a subset of cases and deletes the unselectedcases, such as SELECT IF or SAMPLE.Example*lagfunction.sps.