topic Re: How Can I Get The Lag Function to "Reset" With Each New Batch? in Discussions

How Can I Get The Lag Function to "Reset" With Each New Batch?

jeff_gross — Fri, 10 Jan 2025 21:08:07 GMT

Hello,

I have the following data and I want to use the Lag function to calculate the difference between each result and the result prior to it (the data table is also attached to this message).

I am using JMP 16.

Currently I'm using the following formula in the "Difference" column:

What I can't figure out is how to get the calculation to "reset" once it gets to Batch B. I realize that even with my current formula, only the difference value in row 16 is incorrect, but still I would know to setup the formula so that it works properly within batches.

Does anyone have any suggestions?

Jeff

Re: How Can I Get The Lag Function to "Reset" With Each New Batch?

txnelson — Fri, 10 Jan 2025 21:28:43 GMT

change your formula to

If( :"Time Point (months)"n == 0,
	.,
	:Result - Lag( :Result )
)

Re: How Can I Get The Lag Function to "Reset" With Each New Batch?

jthi — Fri, 10 Jan 2025 21:43:44 GMT

You can also utilize Col Moving Average to get the previous value ( )

:Result- (Col Moving Average(:Result, 1, 1, 0, :Lot Number) * 2 - :Result)

but in your case using something like Jim suggested is most likely better. Also there is Dif function you can use instead of Lag

If( :"Time Point (months)"n == 0,
	.,
	Dif(:Result, 1)
)

Re: How Can I Get The Lag Function to "Reset" With Each New Batch?

jeff_gross — Sat, 11 Jan 2025 01:01:26 GMT

Thank you for the quick replies @txnelson @jthi

Much appreciated!!

Re: How Can I Get The Lag Function to "Reset" With Each New Batch?

hogi — Sat, 11 Jan 2025 08:56:45 GMT

If you need such grouped lag operations frequently, you might have a look at
https://marketplace.jmp.com/appdetails/Normalization+GUI in the Marketplace.

It implemented the N-1 in combination with grouping based on @jthi 's approach:

This takes the pain to remember the exact syntax : )

In addition, the Platform handles Excluded rows automatically.

Re: How Can I Get The Lag Function to "Reset" With Each New Batch?

hogi — Tue, 15 Jul 2025 11:14:18 GMT

- great wish by @FN

-> In JMP19, lag() and dif() can be calculated via Col At () - which provides a grouping option.