Re: How to do a negative pattern?

• To: mathgroup at smc.vnet.net
• Subject: [mg90575] Re: How to do a negative pattern?
• From: dh <dh at metrohm.ch>
• Date: Mon, 14 Jul 2008 05:21:23 -0400 (EDT)
• References: <g5dm6i\$ht4\$1@smc.vnet.net>

```

Hi Steve,

pattern negation is done by: Except.

Daniel

Steven Siew wrote:

> I have used the function DeleteCases which has the format

>

> DeleteCases[expr,pattern]

>

> However what I wanted is a negative pattern like

>

> DeleteCases[expr,negpattern]

>

> But I have no idea how to craft a negative pattern. Alternatively I

> suppose I could do with a DeleteCasesNot function. Something like

> this:

>

> \$ cat file012.out

> Mathematica 5.2 for Students: Microsoft Windows Version

> Copyright 1988-2005 Wolfram Research, Inc.

>

> In[1]:=

> Out[1]= {stdout}

>

> In[2]:= (* Write your mathematica code below *)

>

> In[3]:= mylist={ {1,1},{1,2},{1,3},{2,1},{2,2},{2,3} }

>

> Out[3]= {{1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 2}, {2, 3}}

>

> In[4]:= myselectionA = DeleteCases[mylist,{_,1}]

>

> Out[4]= {{1, 2}, {1, 3}, {2, 2}, {2, 3}}

>

> In[5]:= myselectionB = DeleteCasesNot[mylist,{_,3}]

>

> Out[5]= {{1, 3}, {2, 3}}

>

> In[6]:= (* End of mathematica code *)

>

> In[7]:= Quit[];

>

>

> Does anyone has any idea how I could code up a DeleteCasesNot

> function?

>

--

Daniel Huber

Metrohm Ltd.

Oberdorfstr. 68

CH-9100 Herisau

Tel. +41 71 353 8585, Fax +41 71 353 8907

E-Mail:<mailto:dh at metrohm.com>

Internet:<http://www.metrohm.com>

```

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