Cross Table - Calculate difference between two nested columns - spotfire

Question

I have a cross table as follows -
ColumnA ColumnB ColumnC
+================+===========+===========+===========+===========+===========+===========+
| Store Location | Category1 | Category2 | Category1 | Category2 | Category1 | Category2 |
+================+===========+===========+===========+===========+===========+===========+
| Boston | 200 | 100 | 250 | 230 | 230 | 210 |
+----------------+-----------+-----------+-----------+-----------+-----------+-----------+
| New York | 180 | 150 | 310 | 270 | 240 | 220 |
+----------------+-----------+-----------+-----------+-----------+-----------+-----------+
| Stockholm | 190 | 140 | 180 | 160 | 220 | 210 |
+----------------+-----------+-----------+-----------+-----------+-----------+-----------+
| London | 170 | 140 | 340 | 310 | 420 | 380 |
+----------------+-----------+-----------+-----------+-----------+-----------+-----------+
I want to calculate the difference between two categories for each Columns as follows -
ColumnA ColumnA Diff ColumnB ColumnB Diff ColumnC ColumnC Diff
+================+===========+===========+=====+===========+===========+====+===========+===========+====+
| Store Location | Category1 | Category2 | | Category1 | Category2 | | Category1 | Category2 | |
+================+===========+===========+=====+===========+===========+====+===========+===========+====+
| Boston | 200 | 100 | 100 | 250 | 230 | 20 | 230 | 210 | 20 |
+----------------+-----------+-----------+-----+-----------+-----------+----+-----------+-----------+----+
| New York | 180 | 150 | 30 | 310 | 270 | 40 | 240 | 220 | 20 |
+----------------+-----------+-----------+-----+-----------+-----------+----+-----------+-----------+----+
| Stockholm | 190 | 140 | 50 | 180 | 160 | 20 | 220 | 210 | 10 |
+----------------+-----------+-----------+-----+-----------+-----------+----+-----------+-----------+----+
| London | 170 | 140 | 30 | 340 | 310 | 30 | 420 | 380 | 40 |
+----------------+-----------+-----------+-----+-----------+-----------+----+-----------+-----------+----+
My horizontal axes expression is as follows -
[Axis.Default.Names] NEST [CategoryName]
What custom expression need to use to get it? Appreciate any suggestions.
Thanks a lot.

Answer 1

I haven't found a great way to do this in the cross table. There is one way but it's a little messy depending on how many different values are in the category column and you'd need to know the values in advance. Basically in the cell values axis you would write a custom expression for each column you'd like to see rendered on the horizontal axis. Something like this for each axis:
Vertical Axis:[Store Names]
Horizontal Axis: (Column Names) <--written just like that, or selected from the dropdown on the axis
Values Axis:
sum(if([category]="A", [sales])) as [Sum of A],
sum(if([category]="B", [sales])) as [Sum of B],
sum(if([category]="A", [sales])) - sum(if([category]="B", [sales]) as [delta A-B]
So long as you have "(column names)" on the one of the axes, you can write independent expressions separated by commas on the values axis to back your way into a blend of calculations that aren't applied uniformly to whatever else is on the axis. Its a bit of a slog and can cause issues when new values pop up in your data unexpectedly but it works. Unfortunately it doesn't play nice with marking though. Good luck.