prefix=: 4 : '(->:i.-<.x%2)}.&.> < x {.y'
suffix=: 4 : '( >:i. <.x%2)}.&.> <(-x){.y'
sw=: prefix , <\ , suffix
d=: 5 10 7 8 9 2 1 100 _1 4 3
z=: 5 10 7; 5 10 7 8; 5 10 7 8 9; 10 7 8 9 2; 7 8 9 2 1; 8 9 2 1 100; 9 2 1 100
_1; 2 1 100 _1 4; 1 100 _1 4 3; 100 _1 4 3; _1 4 3
z -: 5 sw d
1
I am not sure what is supposed to happen if n
is greater than the length of the data.
The order of the arguments is switched based on the
principle used for J primitive dyads: x&func is
expected to be a more useful function than func&y .
----- Original Message -----
From: June Kim <[EMAIL PROTECTED]>
Date: Tuesday, January 30, 2007 5:39 pm
Subject: [Jprogramming] sliding window
> Suppose the following data is given
>
> d=: 5 10 7 8 9 2 1 100 _1 4 3
>
> Now suppose a verb that moves a sliding window through the data
>
> d sw 5
>
> The size of the window is always odd. For each item in the given data,
> the window should locate it at the middle point of the window. For
> some items that's nearby boundaries, the window size could be smaller
> than the given.
>
> The result should be
>
> 5 10 7; 5 10 7 8; 5 10 7 8 9; 10 7 8 9 2; 7 8 9 2 1; 8 9 2 1 100;
> 9 2
> 1 100 _1; 2 1 100 _1 4; 1 100 _1 4 3; 100 _1 4 3; _1 4 3
>
> Middle points for the window are 5, 10, 7 ..., 4, 3
>
> What is an easy way for sw?
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