# How to find positive and negative outputs?

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Emily on 9 May 2022
Answered: Emily on 10 May 2022
Hi, I'm trying to have a= dif<-100 or dif>100 with dif being the difference between two numbers, but having trouble getting the negative values to work.
I currently have it as
for i=0:5
dif=struct.smth(:,10) - struct.smth(:,i)
num = (dif <-100) | (100 < dif);
Set.Number =find(num);
end
I have also tried
dif=abs(dif);
num=100<dif;
Set.Number =find(num);
but still only get the positive values to work.
The output when the negative number is triggered is "0x1 empty double column vector"
dpb on 10 May 2022
" negative number is triggered is "0x1 empty double column vector"
It's always possible there ARE no values such that struct.smth(:,10) - struct.smth(:,i) < -100 in which case the empty vector is the expected result.
You need to always remember to write your code when using find and other functions which have such variable-number of outputs where, in fact, one of the valid results is that the result is NIL.
Often placing such code within the try...catch portion and the fixup code for the empty case in the catch...end portion of a try, catch block construct is a slick way to deal with the issue. It may be that the catch block is empty; there's nothing to do in that case.
Also NB:
ixG100 = find(abs(struct.smth(:,10) - struct.smth(:,i)) >100);
will find both cases; you can determine which easily enough when processing the results might be another way to approach it.
I didn't look at all at what really trying to do; just generic comments...

Emily on 10 May 2022
Values were being stored as uint16, changed the inputs to double to get it working.