In SPSS, IF computes a new or existing variable
for a selection of cases. For analyzing a selection of cases, use FILTER or SELECT IF instead.

• Example 1 - Flag Cases Based on Date Function
• Example 2 - Replace Range of Values by Function
• Example 3 - Compute Variable Differently Based on Gender
• SPSS IF Versus DO IF
• SPSS IF Versus RECODE

Data File Used for Examples

All examples use bank.sav, a short survey of bank employees. Part of the data are shown below. For getting the most out of this tutorial, we recommend you download the file and try the examples for yourself.

Example 1 - Flag Cases Based on Date Function

Let's flag all respondents born during the 80’s. The syntax below first computes our flag variable -born80s- as a column of zeroes. We then set it to one if the year -extracted from the date of birth- is in the RANGE 1980 through 1989.

Result

Example 2 - Replace Range of Values by Function

Next, if we'd run a histogram on weekly working hours -whours- we'd see values of 160 hours and over. However, weeks only hold (24 * 7 =) 168 hours. Even Kim Jong Un wouldn't claim he works 160 hours per week!
We assume these respondents filled out their monthly -rather than weekly- working hours. On average, months hold (52 / 12 =) 4.33 weeks. So we'll divide weekly hours by 4.33 but only for cases scoring 160 or over.

Result

Note

We could have done this correction with RECODE as well: RECODE whours (160 = 36.95)(180 = 41.57). Note, however, that RECODE becomes tedious insofar as we must correct more distinct values. It works reasonably for this variable but IF works great for all variables.

Example 3 - Compute Variable Differently Based on Gender

We'll now flag cases who work fulltime. However, “fulltime” means 40 hours for male employees and 36 hours for female employees. So we need to use different formulas based on gender. The IF command below does just that.

Result

Our syntax ends with a MEANS table showing minima, maxima, means and standard deviations per gender per group. This table -shown below- is a nice way to check the results.

The maximum for females not working fulltime is below 36. The minimum for females working fulltime is 36. And so on.

SPSS IF Versus DO IF

Some SPSS users may be familiar with DO IF. The main differences between DO IF and IF are that

• IF is a single line command while DO IF requires at least 3 lines: DO IF, some transformation(s) and END IF.
• IF is a conditional COMPUTE command whereas DO IF can affect other transformations -such as RECODE or COUNT- as well.
• If cases meet more than 1 condition, the first condition prevails when using DO IF - ELSE IF. If you use multiple IF commands instead, the last condition met by each case takes effect. The syntax below sketches this idea.

DO IF - ELSE IF Versus Multiple IF Commands

SPSS IF Versus RECODE

In many cases, RECODE is an easier alternative for IF. However, RECODE has more limitations too.
First off, RECODE only replaces (ranges of) constants -such as 0, 99 or system missing values- by other constants. So something like recode overall (sysmis = q1). is not possible -q1 is a variable, not a constant- but if(sysmis(overall)) overall = q1. works fine. You can't RECODE a function -mean, sum or whatever- into anything nor recode anything into a function. You'll need IF for doing so.

Second, RECODE can only set values based on a single variable. This is the reason why you can't recode 2 variables into one but you can use an IF condition involving multiple variables: if(gender = 0 & whours >= 36) fulltime = 1. is perfectly possible.

You can get around this limitation by combining RECODE with DO IF, however. Like so, our last example shows a different route to flag fulltime working males and females using different criteria.

Example 4 - Compute Variable Differently Based on Gender II

Final Notes

This tutorial presented a brief discussion of the IF command with a couple of examples. I hope you found them helpful. If I missed anything essential, please throw me a comment below.

Thanks for reading!