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
