Re: Applying each element of a vector to each row of a matrix

[Jonathan Webster]

Olaf Till wrote:
> On Sun, Dec 19, 2010 at 12:42:23PM -0600, Jordi Gutiérrez Hermoso wrote:
>   
> > 2010/12/19 Martin Helm <address@hidden>:
> >     
> > > Am Sonntag, 19. Dezember 2010, 18:08:45 schrieb Jordi Gutiérrez Hermoso:
> > >       
> > > > No, no... exponentiate each row or column of a matrix by each element
> > > > of a vector.
> > > >         
> > > Ah - I see, sorry misunderstood completely. I have no good solution for that I
> > > think repmat is the best solution or something similar to that
> > >       
> > Okay, so does my original proposal to extend elementwise operators for
> > the matrix-vector case of compatible dimensions sound silly? I am just
> > wondering why no one else seems to have wanted such an extension so
> > far, so perhaps I'm overlooking something blindingly obvious.
> >     
>
> Well, there is something one already can use, though maybe with too
> much overhead:
>
> octave:4> cat (2, cellfun (@ (x) x .^ ones (4, 1), num2cell (ones (4, 3), 1), 
> "UniformOutput", false){:})
> ans =
>
>    1   1   1
>    1   1   1
>    1   1   1
>    1   1   1
>
> octave:5> 
>
> This example exponenciates each column of ones(4, 3) with the vector
> ones(4, 1).
>
> _____________________
>   
Having done a long stint at work using APL, and wanting to save my time 
rather than the computer's time, I long ago wrote rho.m , implementing  
the arbitrary  reshape properties of the APL operator of that name.  I 
can supply it if anyone is interested.
Here is an example:
octave:1> vv = [1 0 0 0 0]
vv =

  1   0   0   0   0

octave:2> u = rho( vv,4,4)
u =

  1   0   0   0
  0   1   0   0
  0   0   1   0
  0   0   0   1

Jonathan



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