st: calculation 'cross differences'

[Mario Jose <mariojose276@gmail.com>]

Dear all,


I have a sample of companies that are subject to different tax rates,
they are owned by different parent companies. I would like to compute
differences of tax rates within each group and in the perspective of
each company. Below is an example of the database and a view of what I
would like to compute:

group company  taxrate
1                 A              15
1                 B              10
1                 C              20
2                 D              20
2                 E              15
2                 F              14
2                 G              30

The task I need to do is calculate the following regarding for
instance companies A, B and C of group 1:

A=> (15-10) + (15-20)
B=> (10-15) + (10-20)
C=> (20-15) + (20-10)

As I have thousands of companies it is a hard to do this manually, is
there any suggestion on how to handle with this calculations?

I would appreciate any help.

Best regards,
MJ
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