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

11Best Practices and Efficiency TipsCOMPUTE var1=var1+ 5.RECODE var2 (1 thru 5=1) (6 thru 10=2).FREQUENCIES/VARIABLES=var1 var2/STATISTICS=MEAN STDDEV MIN MAX.DESCRIPTIVES/VARIABLES=var1 var2/STATISTICS=MEAN STDDEV MIN MAX.• The transformed values from the two transformation commands that follow theTEMPORARY commandwillbeusedintheFREQUENCIES procedure.• The original data values will be used in the subsequent DESCRIPTIVES procedure,yielding different results for the same summary statistics.Under some circumstances, using TEMPORARY will improve the efficiency of ajob when short-lived transformations are appropriate. Ordinarily, the results oftransformations are written to the virtual active file for later use and eventually aremerged into the saved SPSS data file. However, temporary transformations will notbe written to disk, assuming that the command that concludes the temporary state isnot otherwise doing this, saving both time and disk space. (TEMPORARY followed bySAVE, for example, would write the transformations.)Ifmanytemporaryvariablesarecreated,notwritingthemtodiskcouldbeanoticeable saving with a large data file. However, some commands require two or morepasses of the data. In this situation, the temporary transformations are recalculated forthe second or later passes. If the transformations are lengthy and complex, the timerequired for repeated calculation might be greater than the time saved by not writingthe results to disk. Experimentation may be required to determine which approach ismore efficient.Using Temporary VariablesFor transformations that require intermediate variables, use scratch (temporary)variables for the intermediate values. Any variable name that begins with a poundsign (#) is treated as a scratch variable that is discarded at the end of the series oftransformation commands when SPSS encounters an EXECUTE command or othercommand that reads the data (such as a statistical procedure).Example*scratchvar.sps.DATA LIST FREE / var1.