I have several calculated fields in my workbook. I want to inspect the individual values of the calculated fields to make sure they are doing what I intend them to be.
I tried to do so by clicking View Data for the selected data source. However I noticed some calculated fields (not all) are missing from the table.
What could be the reasons for this? I haven't been able to verify every single one, but my suspicion is the missing ones are calculated fields which involve value from other blended data source. If that is indeed a cause, any suggestions on how I can inspect values of such blended calculated fields?
Okay, first things first. Yes, calculated fields that uses data from other data sources (via blending) won't appear on view data.
Reason is pretty simple, blend data is not an actual hard join query, it's somehow more flexible. For instance, if you have multiple lines of the same key in the blended datasource, a hard join would duplicate (as many times as there are different occurrences of that key on the table) the information from the first table.
Tableau blending data mechanism creates a relation between tables, not a single joined table. And to do so, it requires that all calculated fields using blended data are aggregations, like sum, count or other aggregations.
By definition, an aggregation depends on the level of aggregation you require. Yes you may require the lowest level of aggregation (line by line), but you need to tell Tableau. That's why the field does not appear on View Data. That's because it varies according to aggregation level.
Now, to audit that, I simply recommend you drag the fields that represents the highest level of detail of your database (like id, person, or whatever you have), drag the fields involved and then drag the calculated field. Use all as dimension, and you'll have a table you can export to xls or csv and audit.
Hope it helps