Brian, thank you! That is exactly what I needed.

(] %~ 4 |.!.0 ]) (1+i.4),(1.25+i.4)
1.25 1.125 1.08333 1.0625 0 0 0 0

I should have thought of that. I was thinking of it as a selection solution
and not an array solution. I used shift the other day with my line
detection logic.

I have a well worn print-out of the J Reference card which has it
identified too -- incidentally right where my thumb was holding the paper!

Thanks again
Joe


On Fri, Feb 21, 2014 at 7:17 PM, Brian Schott <[email protected]>wrote:

> Joe,
>
> I think you are looking for  shift as discussed here.
> http://jsoftware.com/help/dictionary/d231.htm
>
> If you think I am right and want more, let me know.
>
>
> On Fri, Feb 21, 2014 at 5:58 PM, Joe Bogner <[email protected]> wrote:
>
> > is there a better way to do this? Calculate change over the 4th or Nth
> > previous cell?
> >
> >
> >  d=.(1+(i.4)),(1.25+(i.4))
> >
> >  d %~ ((# d) {. _4 {. d)
> >
> > 1.25 1.125 1.08333 1.0625 0 0 0 0
> >
> >
> > --
> (B=)
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