Ian's hook
etc=.({.([:{."1(2-/\])^:([:i.#)))^:2
is exactly what I was looking for: an elegant expression without intermediate
names. It remains to de-square the transformation.
Thank you, everybody!
-Bo
--- Den fre 11/6/10 skrev Ian Shannon <[email protected]>:
> Fra: Ian Shannon <[email protected]>
> Emne: [Jprogramming] Polynomial extrapolation
> Til: "[email protected]" <[email protected]>
> Dato: fredag 11. juni 2010 06.29
> Bo,
>
> At the expense of doing the take twice, do the combination
> of take and t twice using power conjunction.
> Note x f^:2 y
> is (x&f)^:2 y
> And all that is required is to stick the x onto the take
> and y onto the t,
> Which hook will do quite nicely.
>
> (( using j701 ))
>
> t=.[: {."1 (2-/\])^:([: i. #)
> NB. Your defn
> of t
> etc =. (({. t)^:2 f.
>
> NB. Power on the hook; fix the definition
> 9!:7 '+++++++++|-'
>
> NB. Use simple chare so as not to screw e-mail
> 9!:3[2
>
> NB. 701 doesn't default
> to box display
> etc
>
> NB.
> Display of defn
> +-------------------------------------------------+--+-+
> |+--+--------------------------------------------+|^:|2|
> ||{.|+--+--------+------------------------------+|| |
> |
> ||
> ||[:|+--+-+-+|+---------------+--+---------+||| | |
> || ||
> ||{.|"|1|||+-+---------+-+|^:|+--+--+-+|||| | |
> || || |+--+-+-+|||2|+-----+-+|]||
> ||[:|i.|#||||| | |
> || || | |||
> ||+-+-+|\|| || |+--+--+-+|||| | |
> || || | ||| |||-|/||
> || || |
> |||| | |
> || || | ||| ||+-+-+|
> || || |
> |||| | |
> || || | |||
> |+-----+-+| || |
> |||| | |
> || || |
> ||+-+---------+-+| |
> |||| | |
> || || |
> |+---------------+--+---------+||| | |
> ||
> |+--+--------+------------------------------+|| | |
> |+--+--------------------------------------------+| |
> |
> +-------------------------------------------------+--+-+
> 21 etc 0 1 4
> 0 1 4 9 16 25 36 49 64 81 100 121 144 169 196 225 256 289
> 324 361 400
>
>
>
>
> Ian Shannon
> Landscape Modelling and Decision Support Section
> Department of Environment, Climate Change & Water
> (NSW)
> PO Box A290 Sydney South
> NSW 1232
> Phone: (02) 99 955 490
> Mob: 0428 296 729
> email: [email protected]
> web: http://www.environment.nsw.gov.au
>
> Please consider the environment before printing my email
>
> ----------------------------------------------------------------------------------------------------------------------------------------------------------------------
> This email is intended for the addressee(s) named and may
> contain confidential and/or privileged information.
> If you are not the intended recipient, please notify the
> sender and then delete it immediately.
> Any views expressed in this email are those of the
> individual sender except where the sender expressly and with
> authority states them to be the views of the Department of
> Environment, Climate Change & Water NSW.
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
