MathGroup Archive 1999

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Re: Parts of a list

  • To: mathgroup at smc.vnet.net
  • Subject: [mg15458] Re: [mg15430] Parts of a list
  • From: "Arnold Knopfmacher" <arnoldk at gauss.cam.wits.ac.za>
  • Date: Mon, 18 Jan 1999 04:22:00 -0500
  • Organization: CAM,University ofthe Witwatersrand
  • Sender: owner-wri-mathgroup at wolfram.com

Regarding your problem (at end of  message), this works In[3]:=
x //.{a___,{b_,0},c___}->{a,c}
Out[3]=
{{2.5,0.5},{0,2}}

Or using Select
In[8]:=
Select[{#},#[[2]]!=0&]& /@x
Out[8]=
{{},{{2.5,0.5}},{},{{0,2}}}
In[9]:=
Flatten[%,1]
Out[9]=
{{2.5,0.5},{0,2}}.
Cheers
Arnold Knopfmacher


> Date:          Wed, 13 Jan 1999 20:57:41 -0500
> From:          "Hossein Kazemi" <kazemi at som.umass.edu>
To: mathgroup at smc.vnet.net

> I have a list (matrix) that looks like this
> 
> x={{1,0},{2.5, .5},{3,0},{0,2}}
> 
> Now I want to eliminate those vectors that have zero for the second
> case. That is, I want to get
> 
> {{2.5, .5},{0,2}}.


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