Some sources show missing values as '0', "-" or "n/a". We always check what each source use for particular data set and unify all those variables into one system. We have two types of missing data in our database:
- N/A - there should be a value in this point in time but for some reason the source didn't deliver it thus the value is missing.
- Skip - there shouldn't be a value due to how the source publish values, so the point in time is omitted i.e.:
- series is Daily but the value is published only for two days in a week;
- series is Monthly, but the source never publish data for January, instead it combined Jan and Feb value together;
- series has history at combined frequency - first Quarterly then Monthly.
Note that 0 in our database is always a representation of a value.
How this impact working with data in application?
For point in time marked as N/A you can choose how application should behave under Conversion settings > Missing value method.
If there is a Skip then that point in time won't appear on Time table at all. However, you can force it to appear by changing on Series list > Observations to 'All points'.