On Mon, Apr 27, 2009 at 2:41 PM, I wrote:
> trap=: (1 :0)
> 'a b c d'=. m
> s=. % _1 1 * _2 -/\ m
> z=. - 0 3 { m
> [: <./ 1 <. 0 >. s * z +/ ]
> )
>
> 2 6 8 10 trap i. 11
> 0 0 0 0.25 0.5 0.75 1 1 1 0.5 0
That was actually the wrong version.
But, I have decided I like my first line there -- it forces an
error when its left argument can not be treated as a sequence
of four.
However, the last line has a minor inefficiency and I should
have said:
trap=: 1 : 0
'a b c d'=. m
s=. % _1 1 * _2 -/\ m
z=. - 0 3 { m
1 <. 0 >. [: <./ s * z +/ ]
)
However, if that first line annoys you too much, an
equivalent form would be:
trap=: 1 : 0
s=. % _2 -/\ m * _1 _1 1 1
z=. - 0 3 { m
1 <. 0 >. [: <./ s * z +/ ]
)
Finally, note that these implementation of trap support treatment
of multiple "trapezoids" at the same time:
(2 6 8 10,. 3 5 7 9) trapa i. 11
0 0 0 0.25 0.5 0.75 1 1 1 0.5 0
0 0 0 0 0.5 1 1 1 0.5 0 0
FYI,
--
Raul
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