Right. Prefer (I.@:= ,) to I.@,@:= since it uses special code.
Henry Rich
On 1/13/2019 2:54 PM, 'Mike Day' via Programming wrote:
You often see this sort of thing, returning pairs of indices of all occurrences:
5 ($@] #.inv I.@,@:=) |: 1 2 3 4,. 2 3 4 5,. 5 4 3 2 ,. 2 3 5 4
1 3
2 0
3 2
You can obviously get the row indices using {:”1 or some such, and you can of
course make the bracketed code a named dyadic verb,
Cheers,
Mike
Sent from my iPad
On 13 Jan 2019, at 17:55, 'Skip Cave' via Programming
<[email protected]> wrote:
I know I can find the location (index) of a specific integer in a vector of
integers using I.
I.5=1 2 3 4 5 4 3 4 5 6 5 6
4 8 10
So I want to find the row index of a specific integer in an array of
integers:
|:1 2 3 4,. 2 3 4 5,. 5 4 3 2 ,. 2 3 5 4
1 2 3 4
2 3 4 5
5 4 3 2
2 3 5 4
5=|:1 2 3 4,. 2 3 4 5,. 5 4 3 2 ,. 2 3 5 4
0 0 0 0
0 0 0 1
1 0 0 0
0 0 1 0
,I. 5=|:1 2 3 4,. 2 3 4 5,. 5 4 3 2 ,. 2 3 5 4
0 3 0 2
The first zero indicates that there is no 5 in the first row. The second
zero gives the index of the 5 in the third row. How can I tell whether the
zero is an index, or a null indicator?
Skip
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