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MathGroup Archive 2006

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Re: Thread function over matrix elements?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg69887] Re: Thread function over matrix elements?
  • From: dh <dh at metrohm.ch>
  • Date: Tue, 26 Sep 2006 05:21:43 -0400 (EDT)
  • References: <efacnv$1v0$1@smc.vnet.net>

Hi Ben,
you must understand level specifications, then all becomes clear:
n indicates level 1..n, {n} indicates level n
therefore, what you want is: Map[f, mat, {2}], if you say: Map[f, mat, 
2], f is appled to level 1 and 2, hardly what you want.

Apply does not work, because you can not replace the head of an atom. 
Neither does Thread because Thread has no level-control.
Daniel

ben wrote:
> Dear all,
> 
> how do I thread a function over all elements of a matrix?
> This piece of code works, but I doubt its the way i am supposed to do
> this
> 
> mat=Table[i+j,{i,0,2},{j,0,2}]
> 
> Map[Map[f[#]&,#]&,mat]
> 
> I tried
> 
> Map[f[#]&,mat,2]
> Apply[f[#]&,mat,2]
> Thread[f[mat]]
> 
> but they give weird results.
> 
> Cheers
> Ben
> 


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