My SPSS Syntax code below does not produce the results intended. Even when reason is equal to 15 or 16, it will flag ped.crossing.with.signal to 1.
COMPUTE ped.crossing.with.signal = 0.
IF ((ped.action = 1 | ped.action = 2) AND (reason ~= 15 | reason ~= 16)) ped.crossing.with.signal = 1.
EXECUTE.
When I do it like this, it works... but why?
COMPUTE ped.crossing.with.signal = 0.
IF (ped.action = 1 | ped.action = 2) ped.crossing.with.signal = 1.
IF (reason = 15 | reason = 16) ped.crossing.with.signal = 0.
EXECUTE.
It's not a wonky result, but rather the correct application of boolean algebra which is explained by De Morgan's Laws.
The expression (reason ~= 15 | reason ~= 16) is equivalent to ~(reason = 15 and reason = 16) which in this case can never evaluate to false (because a single variable can't hold two values). Logically, the correct expression to use would be (reason ~= 15 & reason ~= 16) or ~(reason = 15 | reason = 16) although as pointed out already using the any function is more straightforward.