Finding Null Values

[Mouser]

Having difficulty filtering on NULL values.  Inputting any numerical value in the "Months Since Last Delinquency" range fields excludes all returns without a value so trying to create a custom query.   

I know the language is not quite SQL but I cannot find the right syntax to make the query work.  I am attempting to filter only loans with a null value in the field mthsSinceLastDelinq. 

Tried several variations in the "Custom Filter - Experts Only" field including:
   mthsSinceLastDelinq isnull
   mthsSinceLastDelinq is null

PLS Version 7.904

Any suggestions appreciated.

Thanks, Mouser

[sociallender]

Close, but NAs are used for missing values.  Here is the code:

is.na(mthsSinceLastDelinq)

HTH, SL

[TravelingPennies]

Wonderful, that did it!
Appreciate the ongoing support.  Love the tool.