Why isn't my code flagging variables correctly?

[confused_saser]

I am trying to flag one of my variables (tsi_days) only when it is less than 0. However my code seems to also be flagging my variable when it is also missing. 

this is my code:

if tsi_days < 0 then tsi_exclude=1;
	else if tsi_days=. then tsi_exclude=0;
	else tsi_exclude=0;

What am I doing wrong?

this is the output:

[PGStats · Accepted solution]

In SAS, a missing numeric value is < 0. Thus, you must test

tsi_exclude = tsi_days < 0 and not missing(tsi_days);

[data_null__]

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@confused_saser wrote:

I am trying to flag one of my variables (tsi_days) only when it is less than 0. However my code seems to also be flagging my variable when it is also missing. 

this is my code:

if tsi_days < 0 then tsi_exclude=1;
	else if tsi_days=. then tsi_exclude=0;
	else tsi_exclude=0;

What am I doing wrong?

this is the output:

---

That's because missing is less than 0.  Do the test for missing first.

[confused_saser]

@data_null__ what do you mean do the test for missing? I'm not sure I understand what that means

[data_null__]

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@confused_saser wrote:

@data_null__ what do you mean do the test for missing? I'm not sure I understand what that means

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In your code you have a test for missing

if tsi_days < 0 then tsi_exclude=1;
	else if tsi_days=. then tsi_exclude=0;
	else tsi_exclude=0;

I'm saying do that first and then do the test for TSI_DAYS < 0.

[LaurieF]

That's because SAS flags missing values as less than negative, so your first condition is flagging them as such.

One way of doing your code as you wish is to use the sign function. This returns values of -1 for negative, 0 for zero and 1 for positive. Or you can change the order of your conditions (I use select because it makes for ease of reading)

select;
   when(missing(tsi_days))
       tsi_exclude = 0;
   when(tsi_days < 0)
       tsi_days = 1;
   otherwise 
       tsi_exclude = 0;
   end;