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
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.
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Assuming the data are sorted:
If(Row() == 1, counter = 1); If(:group == Lag(:group), counter, counter = counter + 1); counter
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Here's the formula version of Jim's answer.
If( Row() == 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.