Formula for automatic counter by group of rows

sornasst

Hi,

I would like to write a formula in JMP 11.1 that will automatically create a counter by  group of rows as shown in the table below

Group	Counter
ABC	1
ABC	1
ABC	1
ABC	1
CDE	2
CDE	2
EFG	3
EFG	3
EFG	3
GHI	4
GHI	4
GHI	4

I suspect that the Dif() and/or Lag() functions have something to do with this but I have not been able to implement it.

Note: this counter by group of rows is very easy to implement in Excel

Thank you for your help.

txnelson

Assuming the data are sorted:

If(Row() == 1, counter = 1); If(:group == Lag(:group), counter, counter = counter + 1); counter