a generic approach,
([: (0 ~: 3 | i.@:#@{.)`]} ] ,:~ >: ) i.20
1 1 2 4 4 5 7 7 8 10 10 11 13 13 14 16 16 17 19 19
can be turned into conjunction where u = verb you want to apply, n is the
interval
fornth1 =: 2 : '([: (0 ~: n | i.@:#@{.)`]} ] ,:~ u )'
except your desired result does not actually literally apply just nth element.
Rather, in your example, the 0th and 2nd indexes are repeatedly incremented.
If instead just the nth elements are to be processed then the conjunction is:
fornth =: 2 : '([: ((n-1) = n | i.@:#@{.)`]} ] ,: u )'
>: fornth 3 i.20
0 1 3 3 4 6 6 7 9 9 10 12 12 13 15 15 16 18 18 19
>: fornth 3 i.20
On Wednesday, January 15, 2020, 09:30:38 p.m. EST, Skip Cave
<[email protected]> wrote:
How does one apply a monadic verb repetitively to every nth element of a
one1-dimentional array?
For example:
]a=.i.20
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19
n=.3
NB. Design u to increment every nth integer in a:
u=.??:<??
n u a
1 1 2 4 4 5 7 7 8 10 10 11 13 13 14 16 16 17 19 19
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