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Re: List Manipulation (2)

• To: mathgroup@smc.vnet.net
• Subject: [mg10676] Re: List Manipulation (2)
• From: Allan Hayes <hay@haystack.demon.co.uk>
• Date: Fri, 30 Jan 1998 04:24:15 -0500
• References: <69nbfq$89h@smc.vnet.net> <6ahlgq$p76@smc.vnet.net>

Paul.Hanson@colorado.edu wrote:
> If I have a list of n lists, and want to
> get rid of all the even ones how would I go about doing  this?  That
> is, {{n1},{n2},.....{2n}} converted to {{n1},{n3}...{2n-1}}. 

Paul:

Here is another way:

lst = {{a},{b,c},{d},{e,f,g},{h,a},{k,l,{m,n}},{o,p,q}};

lst[[Table[i,{i,1,Length[lst],2}]]]

{{a},{d},{h,a},{o,p,q}}

It's slightly slower than my earlier posting, which used Partition, but
the increased flexibility is valuable.

tst = Table[i, {10000},{i,Random[Integer,100]}];

Partition[tst,1,2,Sequence];//Timing//First

0.166667 Second

tst[[Table[i,{i,1,Length[tst],2}]]];//Timing//First

0.183333 Second


-- 
Allan Hayes
Mathematica Training and Consulting
Leicester, UK
hay@haystack.demon.co.uk
http://www.haystack.demon.co.uk
voice: +44 (0)116 271 4198
fax: +44 (0)116 271 8642