>
> On Sat, Jan 19, 2019 at 8:40 AM Roger Hui <[email protected]>
> wrote:
>
> > If the keys are numeric you can multiply the ascending column by 1 and
> > the descending one by _1, and then apply /: .
> >
It is not enough to multiply with 1 or _1 for ascending or descending columns.
You might have to reorder the columns as well.
Suppose the 3-column matrix x with
|:x=. ,/^:2 >{3#<i.3
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2
0 0 0 1 1 1 2 2 2 0 0 0 1 1 1 2 2 2 0 0 0 1 1 1 2 2 2
0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2
has to be sorted ascending by column 0, descending by column 2 and ascending
by column 1, in that order.
Multiplying columns by 1 1 _1 and sorting would deliver
|:1 1 _1( ]/: *"1 ) x
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2
0 0 0 1 1 1 2 2 2 0 0 0 1 1 1 2 2 2 0 0 0 1 1 1 2 2 2
2 1 0 2 1 0 2 1 0 2 1 0 2 1 0 2 1 0 2 1 0 2 1 0 2 1 0
Whereas this is (the transposed of) what we want
|: 1 1 _1( ]/: *"1)&.:(0 2 1&C."1) x
0 0 0 0 0 0 0 0 0 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2
0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2 0 1 2
2 2 2 1 1 1 0 0 0 2 2 2 1 1 1 0 0 0 2 2 2 1 1 1 0 0 0
R.E. Boss
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