Re: Parts of a list

• To: mathgroup at smc.vnet.net
• Subject: [mg15457] Re: Parts of a list
• From: Rolf Mertig <rolf at mertig.com>
• Date: Mon, 18 Jan 1999 04:21:58 -0500
• Organization: Mertig Research & Consulting
• References: <77jkve\$304@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```Hossein Kazemi wrote:
>
> 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}}.
>
> Is there a quick way of doing this?
> I tried to apply Select to this but could not get it to work.
>
>
> Hossein Kazemi
> UMass
> kazemi at som.umass.edu

In[1]:=  x={{1,0},{2.5, .5},{3,0},{0,2}};

In[2]:= Select[x, MatchQ[#, {_,a_/;a=!=0}]&]

Out[2]= {{2.5, 0.5}, {0, 2}}

In[3]:= Cases[x, {_, a_/;a=!=0}]

Out[3]= {{2.5, 0.5}, {0, 2}}

--

Rolf Mertig
Mertig Research & Consulting
Mathematica training and programming Development and distribution of
FeynCalc  Amsterdam, The Netherlands
http://www.mertig.com

```

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