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Re: PSPP-BUG: Inconsistency with SPSS when setting missing strings value
Re: PSPP-BUG: Inconsistency with SPSS when setting missing strings values with a number
Thu, 17 Sep 2020 11:34:16 +0200
On Wed, Sep 16, 2020 at 05:52:22PM -0700, Dana Williams wrote:
I'm not sure if I've discovered a small bug or have simply made an
unusual user error.
It sounds to me like a user error, but I'm not sure that I've fully
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.
If I had to hazard a guess, perhaps you inadvertently set the missing value
the wrong thing. It's worth reminding you that all strings in spss/pspp have
a fixed length (default is 8). So for a string variable of length 8, there
can never be a value of "0". But there can be a value "0 ". Normally,
pspp should right pad shorter values, so that if you enter "0" the value which
actually gets entered is "0 ", but if you inadvertently type " 0", then
you will get " 0 ".
While in SPSS, I used the following syntax to try to reset the missing
values to 0:
missing values [VARIABLENAME] (0).
I would have expected to see an error here, if VARIABLENAME is a string
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.
After you set the missing value, try typing "DISPLAY DICTIONARY." This will
show you what the system's idea of a missing value is.
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.
Please do. And please run "DISPLAY DICTIONARY." on both datasets, and post
the output you get.