Do you use lag(x)?

[#1]

... seems that this is no longer possible: 

tested with JMP18.1.1

JMP17:

[#2]

Seems to work fine in all the versions I tried, including 18.1.1.

[#3]

Ok, good.

And kind of strange ...

So, it's neither 100% gone - nor 100% working.
what makes the difference ?

PC vs. Mac?
... I will check my preferences - and compare with more colleagues.

[#4 · Accepted solution]

The good thing:
It's not a general issue of "Lag"

... it seems to be caused by:

When I generate the Formula this way, the entries are empty.
When I create a new column and add the formula afterwards, the values are calculated.

added: video with different ways to generate the formula column

1. new formula column: add lag via click      -> fail
2. new formula column: add lag manually    ->  fail
3. new formula column: delete code and write again    -> fail
4. new column -> add formula manually -> works
5. new column -> add formula column via click and write (like #2) -> works

[#5]

I submitted a ticket to JMP support: TS-00182750
let's see ...

[#6 · Accepted solution]

Seems like JMP will incorrectly evaluate the "missing" argument to Empty()

// Transform column
Data Table("Big Class") << Apply Formula(
	Columns(:weight),
	Formula(Lag(:weight, Empty())),
	Output(New Formula)
);

If you use Lag under Row this doesn't happen as it uses other method to create the column

// New formula column: Lag[weight]
Data Table("Big Class") << New Formula Column(
	Operation(Category("Row"), "Lag"),
	Columns(:weight)
);

Edit: And it does happen with other functions too (at least with Dif but there could be other)

// Transform column
Data Table("Big Class") << Apply Formula(
	Columns(:weight),
	Formula(Dif(:weight, Empty())),
	Output(New Formula)
);

[#7]

Good point, thanks @jthi for digging deeper.

I never paid attention and noticed the 2 ways formula editor displays optional arguments:

1. explicit:
   
   
   
2. not [just in the description]: