Excel Power Query Select value from previous row

[dicken]

Hi
I've been trying to use Table.SelectRows to get a value from the previous row, I've got as far as a list of values,

= Table.AddColumn(#"Changed Type", "Custom",  (A)=>

 Table.SelectRows( #"Changed Type" ,(B)=> B[Date] < A[Date] )[Units]  )

Which returns a list of the units 0 in first 1 item in second 2 items in third position, I've been trying to return the first list item for row 1, second list item for row 2 and so on, I thought of
l

 } )

It may not be possible I'd be interested in any ideas,

So here I wold like to just have the second item from the list 3.

Richard.

 

[JGordon11]

An example

let
    Source = Table.FromColumns({{0..9}, List.Dates(#date(2022,10,28), 10,#duration(2,0,0,0))}, {"Index", "Date"}),
    Result = Table.AddColumn(Source, "Previous Date", each try Source{[Index]-1}[Date] otherwise null)
in
    Result

 

[dicken]

An example

let
    Source = Table.FromColumns({{0..9}, List.Dates(#date(2022,10,28), 10,#duration(2,0,0,0))}, {"Index", "Date"}),
    Result = Table.AddColumn(Source, "Previous Date", each try Source{[Index]-1}[Date] otherwise null)
in
    Result

Thanks,
RD

 

[dicken]

An example

let
    Source = Table.FromColumns({{0..9}, List.Dates(#date(2022,10,28), 10,#duration(2,0,0,0))}, {"Index", "Date"}),
    Result = Table.AddColumn(Source, "Previous Date", each try Source{[Index]-1}[Date] otherwise null)
in
    Result

Thanks again, it's much more simple ( in a good way) than many, and no need for multiple index columns and merging,
the two way looking up in pq is something where I'm alway putting things in the wrong place or forgetting braces,

RD