Dynamically create new fields with null values

[Newt]

I am comparing values for a few dozen fields, this month vs. last month.  

When there's a new item this month, there is no "last month field" to compare it to.

This crashes the flow when the logic tries to compare "Sales" with "Sales Previous Month"... since the Sales Previous Month field does not exist for new items.

For items with no previous month, how can I create a dynamically changing set of fields for last month, with null or zero values?  I'd Append this empty set to the current month's fields.

I'd like this to be dynamic because the users likely will decide to monitor different fields as time passes.

Thanks for any help!

[Qiu]

@Newt 
Is it possible for you to provide sample input files and sample output?

[Yoshiro_Fujimori]

Hi @Newt ,

If the column names follows a specific rules like [name] vs. [name_Previous], you can use Cross Tab as below.

Input Data

RecordID	ItemA	ItemA_Previous	ItemB	ItemB_Previous	ItemC
1	10	11	20	22	10
2	20	22	40	42	20
3	30	33	60	62	30
4	40	44	80	82	40
5	50	55	100	102	50

Output Data

RecordID	Name	Current	Previous	Diff
1	ItemA	10	11	-1
1	ItemB	20	22	-2
1	ItemC	10
2	ItemA	20	22	-2
2	ItemB	40	42	-2
2	ItemC	20
3	ItemA	30	33	-3
3	ItemB	60	62	-2
3	ItemC	30
4	ItemA	40	44	-4
4	ItemB	80	82	-2
4	ItemC	40
5	ItemA	50	55	-5
5	ItemB	100	102	-2
5	ItemC	50

Workflow

Formula Tool
[Cur_Prev] = IF EndsWith([Name], "_Previous") THEN "Previous" ELSE "Current" ENDIF
[Name] = REGEX_Replace([Name], "_Previous$", "")

[dreldrel]

I like your idea @Yoshiro_Fujimori! I used to use Python tool to address this kind of task, but now I have a much easier to do it :)