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I'm trying to assign +1 values to a 'trade' series when my 'res' (=residual) series is greater than standard deviation (=s) and -1 when my 'res' series less than negative standard deviation

if res>s then
series trade=1
else
if res<-s then
series trade=-1
endif
endif

but getting a message "NA found in matrix IF RES>S then"

Is there a way to avoid the NA message?

use @recode instead.

@recode will work for the first time, but when I use it for the second, it will overwrite the first results.
Any other suggestions?

Thank you for the help