Oops, not sum, but (-/) for determinant. Using sum there gives the permanent of a matrix. Sorry, I'm just waking up...
https://en.wikipedia.org/wiki/Determinant https://en.wikipedia.org/wiki/Permanent Thanks, -- Raul On Fri, Sep 15, 2017 at 8:23 AM, Raul Miller <rauldmil...@gmail.com> wrote: > http://www.jsoftware.com/help/dictionary/d300.htm is the formal > specification for dot. But assumes perhaps too much of the reader's > math background. http://code.jsoftware.com/wiki/Vocabulary/dot is more > long winded, but apparently not satisfying for you, either? > > Anyways, -/ .* is the determinant of a matrix. In your + .- example, > you're performing the same structural operation (which bill lam has > mentioned), but replacing sum (+/) with complex conjugate (+) and > replacing multiplication (*) with subtraction (-). Probably not an > incredibly useful operation, but since you got rid of the sum you'll > have a lot of dimensions in your result. (Note also that complex > conjugate winds up just being an identity function on real numbers.) > > I hope this helps... > > -- > Raul > > > On Fri, Sep 15, 2017 at 7:37 AM, Rudolf Sykora <rudolf.syk...@gmail.com> > wrote: >> On 15 September 2017 at 12:50, Erling Hellenäs <erl...@erlinghellenas.se> >> wrote: >>> http://code.jsoftware.com/wiki/Vocabulary/dot >>> >>> http://www.jsoftware.com/help/dictionary/d300.htm >> >> unfortunately, I cannot find a serious definition at either place. >> (And I still think the definition is not present in the mentioned >> dictionary.) >> >> E.g. what will >> + . - i. 2 3 4 >> do and why? >> >> Thanks >> Ruda >> ---------------------------------------------------------------------- >> For information about J forums see http://www.jsoftware.com/forums.htm ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
