How to use Dif/Lag function by Column group

[#1]

Hi JMP community folks,

I have a data table with four columns as Box, iClass, BinPos, and Slot.   iClass means 24 level of products, BinPos means the Box location in the sorting equipment and Slot indicated which slot position the product be placed in the box. The Box is designed to hold a max quantity of 100 product, after that a new empty box would be placed in. In order to check the product is be placed in the right box and the Slot increment is exactly by "1" (because sometime I do manually observed the slot increment increase >1 or increment=0, which meant the placing machine having issues),I tried to use the dif/lag function to check the increment. However, the dif/lag formula is not allowing me the add a function to group by column of Box. The Box is actually the unique identifier.

A formula like Dif(:Slot,1) can tell me the difference b/w a certain with respect to the row before it. However, the rows are mixed by with different Box because of difference level of product belong to iClass column.

I am hoping to have a formula like Dif(:Slot, 1, :Box) to work out. Can any expert provide some clues to work this out? A example table is attached for investigation.

Many Thanks in advance

Box	iClass	BinPos	Slot
72813_2	11	11	64
73213_2	15	15	2
73213_2	15	15	3
73213_2	15	15	4
73213_2	15	15	5
73213_2	15	15	6
73213_2	15	15	7
73213_2	15	15	8
73214_2	14	14	1
73214_2	14	14	2
73214_2	14	14	3
73214_2	14	14	4
73214_2	14	14	5
73214_2	14	14	6
73213_2	15	15	9
73214_2	14	14	7
73213_2	15	15	10
73213_2	15	15	11
73213_2	15	15	12
73213_2	15	15	13
73213_2	15	15	14
73213_2	15	15	15
73214_2	14	14	8

[#2]

Jim, 

I take it back - Formula wasn't working because it didn't know Get Rows Where expression. As soon as I changed the colum type (it was a date, so I really didn't care) to Numeric, it worked, even though it still doesn't like the Get Rows Where.

Basically, what I'm trying to do is to find the previous date by Column.

I have a table of parts replacement history on different tools:

Tool	Part	Install Date	Remove Date
Tool A	Part 1	03/03/2015	???
Tool B	Part 1	04/04/2015	???
Tool A	Part 2	05/05/2015	???
Tool A	Part 1	06/06/2015	???
Tool A	Part 2	07/07/2015	???

So, for the same tool and the same part, I need to get the NEXT install date and put it as a Remove Date for current part.

Now, I'm not sure how do you make sure that the it actually looks up the NEXT date. Formula works with the minimal modifications as I can tell on the limited observations, but as far as I understand the formula, it wouldn't...

Could you please help me with clenaing this up?

Thanks, 

M.

[#3]

Here is a little script that should give you the results you want for the Remove Date

Names Default To Here( 1 );
dt = Current Data Table();

// Add a sequence column to capture the current
// order of the data table
dt << New Column( "tableorder", formula( Row() ) );
// Convert the values in the tableorder column to real values
dt:tableorder << delete formula;

// Sort the table in ascending order
dt = dt << Sort(
	By( :Tool, :Part, :Install Date ),
	Order( Ascending, Ascending, Ascending ),
	replace table( 1 )
);

// Create the Remove Date Column
dt << New Column( "Remove Date", Format( "m/d/y", 10 ) );

// Loop across all of the rows and set the Remove Date
For( i = 2, i <= N Rows( dt ), i++,
	If( :Tool[i] == :Tool[i - 1] & :Part[i] == :Part[i - 1],
		:Remove Date[i - 1] = :install Date[i]
	)
);

// Sort the table back to original order
dt = dt << Sort( By( :tableorder ), Order( Ascending ), replace table( 1 ) );

// Remove the tableorder column
dt << delete columns( "tableorder" );