How can I loop through variables in SPSS? I want to avoid code duplication

Question

Is there a "native" SPSS way to loop through some variable names? All I want to do is take a list of variables (that I define) and run the same procedure for them:

pseudo-code - not really a good example, but gets the point across...

for i in varlist['a','b','c']
do
  FREQUENCIES VARIABLES=varlist[i] / ORDER=ANALYSIS.
end

I've noticed that people seem to just use R or Python SPSS plugins to achieve this basic array functionality, but I don't know how soon I can get those configured (if ever) on my installation of SPSS.

SPSS has to have some native way to do this...right?

Answer 1

There are two easy solutions for looping through variables (easier compared to using Python in SPSS).

1) DO REPEAT-END REPEAT

The draw back is that you can use DO REPEAT-END REPEAT mainly only for data transformations - for example COMPUTE, RECODE etc. Frequencies are not allowed. For example:

DO REPEAT R=REGION1 TO REGION5.
COMPUTE R=0.
END REPEAT.

2) DEFINE-!ENDDEFINE (macro facility)

You can do Frequencies in a loop of variables using macro command. For example:

DEFINE macdef (!POS !CHAREND('/'))
!DO !i !IN (!1)
frequencies variables = !i.
!DOEND
!ENDDEFINE.

macdef VAR1 VAR2 VAR3  /.

Answer 2

If I understand the question correctly, there may be no need to use a looping construct. SPSS commands with a VARIABLES subcommand like FREQUENCIES allow you to specify multiple variables.

The basic syntax for the FREQUENCIES is:

FREQUENCIES
    VARIABLES= varlist [varlist...] 

where [varlist] is a single variable name, multiple space-delimited variable names, a range of consecutive variables specified with the TO keyword, the keyword ALL, or a combination of the previous options.

For example:

FREQUENCIES VARIABLES=VARA

FREQUENCIES VARIABLES=VARA VARB VARC

FREQUENCIES VARIABLES=VARA TO VARC     

FREQ VAR=ALL

FREQ VAR=VARA TO VARC VARM VARX TO VARZ

See SPSS Statistics 17.0 Command Syntax Reference available at http://support.spss.com/ProductsExt/SPSS/Documentation/SPSSforWindows/index.htm

Note that it's been years since I've actually used SPSS.

Answer 3

It's more efficient to do all these frequencies on one data pass, e.g., FREQUENCIES a to c. but Python lets you do looping and lots of other control flow tricks.

begin program.
import spss
for v in ['a','b','c']:
  spss.Submit("FREQUENCIES " + v)
end program.

Using Python requires installing the (free) Python plugin available from SPSS Developer Central, www.spss.com/devcentral.

You can, of course, use macros for this sort of things, but Python is a lot more powerful and easier once you get the hang of it.