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Re: MapThread over ragged arrays

  • To: mathgroup at smc.vnet.net
  • Subject: [mg83435] Re: MapThread over ragged arrays
  • From: Bill Rowe <readnewsciv at sbcglobal.net>
  • Date: Tue, 20 Nov 2007 03:55:10 -0500 (EST)

On 11/19/07 at 6:13 AM, bravi at cs.washington.edu (Ravi
Balasubramanian) wrote:

>I have two matrices that are ragged.

>mat1  = {{1, 2}, {2, 3, 4}, {5, 6}}
>mat2 = {{a, b}, {b, c, d}, {e, f}}

>I have to Map a function f at level 2.  So that I have

>{
>{f[1,a],f[2,b]},
>{f[2,b], f[3,c], f[4,d]},
>{f[5,e],f[6,f]},
>}

>MapThread seems to thread only over full arrays, and so I cannot
>thread over level {2}.  I know I can I do this using two MapThreads
>(each at level 1), but that seems unnecessary.  Thread seems to
>apply the head to each value, and if the head does not match, the
>value is repeated (which might not be necessary).  Seems like a
>simple thing to do.  Any ideas?

This seems to do what you want

In[3]:= MapThread[Thread[f[##]] &, {mat1, mat2}]

Out[3]= {{f[1, a], f[2, b]}, {f[2, b], f[3, c], f[4, d]}, {f[5, e],
   f[6, f]}}
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