Johann Hibschman-4 wrote:
>
> [...]
>
> Here's a simple question from a rank beginner:
>
> Expressing polynomials as, for example,
>
> +/1 _1 1*x^i.3
>
> works well, as long as x is a scalar. If x is of higher rank, this
> stops working.
>
Well known efficient representation of polynomial assuming
right-to-left order of evaluation is:
c1+x*c2+x*c3+x*c4+...+x*cn === (+ x * ])/ c === (+ x&*)/ c
We can define an adverb P that does this kind of computation:
P=:(&*)(+`)(`:6)/
1 2 3 P
(+ 1 2 3&*)/
1 2 3 P 1 2 3 4
10 49 142
1 2 3 p.~ 1 2 3 4
10 49 142
1 2 3 P("1) 1 2 3 4,:4 3 2 1
10 49 142
10 26 58
My somewhat brute-force solution is to manually set the
> rank used, as in:
>
> x=:2 3 5
> +/1 _1 1*x^_ 0 i. 3
>
> Is this good style? Is there a better way?
>
> Thanks, and pardon the pun,
> Johann
>
> ----------------------------------------------------------------------
> For information about J forums see http://www.jsoftware.com/forums.htm
>
>
--
View this message in context:
http://old.nabble.com/simple-polynomials-tp29486977s24193p29497553.html
Sent from the J Programming mailing list archive at Nabble.com.
----------------------------------------------------------------------
For information about J forums see http://www.jsoftware.com/forums.htm
