[DDI-users] DDI-users Digest, Vol 105, Issue 6 (SAS/Stata extended missings)

[Bob McConnaughey]

i suspect i'm belaboring the obvious here, but here's how SAS treats
numeric missings
SAS numeric missings appear to be "character strings" - but they are
treated, within SAS (and Stata i believe) as "invented" numbers, smaller
than the "smallest" negative number.  eg -1*10**10000 > .z > .a > . > ._ ;
 (though i don't think i've ever seen "._" used).  However their great
virtues are: 1. As "known" missings they automatically get excluded from
computations involving the variable they represent.  And, like any other
value (character or numeric) the can be described using formats..  That is
when you do, say, a frequency proc and assign formats to the missing you'd
see something like:
time_to_pregnancy1
value timetopg
  1-2 = '1-2 mos'
  3-5 = '3-5 mos'
  6-12 = '6-12 mos'
 13-high = ' > 1 yr'
 .r         = 'Refused'
 .d        = "don't  remember"
 .m       = 'set to missing by rule'
.          = 'other missing'
;
Value labels are the equivalent SPSS feature (i think..i haven't used SPSS
in 35 yrs) and even now most of our original questionnaires use "out of
range" numbers for special missing values.  But the number of times
post-docs and researchers have come up with funky basic descriptive
statistics because, oh, "99" was used for a missing value for
"height_inches" is well nigh uncountable.  And matters are getting worse
because there's a general tendency to not use codebooks any more;  instead
projects rely on "annotated questionnaires" and SAS "proc contents" I am
very much hoping to get people here to go back to using codebooks and the
various DDI products SHOULD be convincing. (well, convincing for people
other than the small group of reproductive epidemiology researchers I work
with most closely).

thanks for the responses!
Bob McC....

"At times like this, an adult needs a drink."
Dance, Dance, Dance.  H. Murakami
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