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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.

Re: Formula for automatic counter by group of rows

Here's the formula version of Jim's answer.

If( Row() == 1,

1,

Lag( :Counter Formula, 1 ) + (Lag( :Group, 1 ) != :Group)

)

Notice that the addition step takes advantage of the fact that comparisons result in a 1 or 0 for true or false. So, we can compare the value of Group in the current row to the previous row and if they are not equal (!=) it will add 1.

-Jeff

Re: Formula for automatic counter by group of rows

Assuming the data are sorted:

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