Re: How to do a negative pattern?
- To: mathgroup at smc.vnet.net
- Subject: [mg90578] Re: [mg90562] How to do a negative pattern?
- From: Bob Hanlon <hanlonr at cox.net>
- Date: Mon, 14 Jul 2008 05:21:58 -0400 (EDT)
- Reply-to: hanlonr at cox.net
DeleteCasesNot is just Cases
mylist = {{1, 1}, {1, 2}, {1, 3}, {2, 1}, {2, 2}, {2, 3}};
myselectionB = Cases[mylist, {_, 3}]
{{1, 3}, {2, 3}}
Bob Hanlon
---- Steven Siew <stevensiew2 at gmail.com> 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?