PSPP-BUG: Inconsistency with SPSS when setting missing strings values with a number

[Dana Williams]

I'm not sure if I've discovered a small bug or have simply made an 
unusual user error.

Background: Every semester I have my statistical analysis class compose 
a set of survey questions for themselves, answer the questions, then use 
the responses to create a dataset. My university has SPSS available, but 
not everyone can get it working (esp. now that classes are all online), 
so I recommend using PSPP as an alternative. Since I'm running Ubuntu 
bionic at home, this is perfect for me.

The problem: In the PSPPire GUI, we marked missing values for string 
variables with a zero (i.e., a "0" without the quote-marks) and then 
declared them to be missing as discrete values via the Variable View. I 
presumed this would work fine. When running frequencies in PSPP, all 
cases marked with a 0 successfully showed up as missing. When using this 
dataset--wholly created in PSPP during class time--in SPSS, however, 
students found that the cases that should have been missing were not 
marked as such, and just appeared in output tables as zeroes. I borrowed 
my partner's laptop and opened our dataset in SPSS and found the same 
problems the SPSS-using students had. SPSS showed missing values of 0 
for those variables in the Variable View, so I was confused why they 
were nor marked as missing when doing a frequency test.

While in SPSS, I used the following syntax to try to reset the missing 
values to 0:

missing values [VARIABLENAME] (0).

This didn't change any of the frequency results. But, I wondered if SPSS 
might have thought that the missing value was set to the numeral 0, as 
opposed to a string of 0, so I used:

missing values [VARIABLENAME] ("0").

Instantly the values were caught as missing. In other words, I think 
that our use of the number 0 in PSSP didn't appropriately set itself as 
a character/string of "0"... or SPSS couldn't recognize this with the 
PSPP-created dataset. Or maybe, despite these variables being strings, 
we were somehow inappropriately allowed to enter a number value for 
missing in the Variable View.

For myself, I was using PSPPire 1.0.1 and SPSS 27.

I can share our PSPP-created and SPSS-saved/fixed dataset if this would 
help figure out the problem.

In solidarity,
Dana


--
Dana Williams, Ph.D.
Associate Professor
Department of Sociology
California State University, Chico
http://dmwilliams.yourweb.csuchico.edu/