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MathGroup Archive 2005

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comparing two lists

  • To: mathgroup at smc.vnet.net
  • Subject: [mg54284] comparing two lists
  • From: Curt Fischer <tentrillion at gmail.NOSPAM.com>
  • Date: Wed, 16 Feb 2005 14:36:02 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Dear Group:

I want to write a function that accepts a n-vector and an n x m matrix. 
It should return a list of positions in the matrix where mat[[i,j]] > 
vec[[i]].  For example,

In[287]:=
vec=Table[Random[],{2}]

Out[287]=
{0.482259,0.314393}

In[288]:=
mat=Table[Table[Random[],{4}],{2}]

Out[288]=
{{0.183706,0.758693,0.462242,0.170041},{0.457054,0.349658,0.805455,0.127763}}

I would like myFunc[] to return {{2},{1,2,3}}.

How could I write this as a pure function?  Ideally I would like to be 
able to Map or Apply my function to the list {mat, vec} and get my result.

Something like

Position[#1,_?(#>#2&)]&@@{mat,vec}

is doomed to fail because the PatternTest required in Position[] messes 
up the slotting of the other arguments.

Ideas?  How do you nest pure functions?

-- 
Curt Fischer


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