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Re: problem of syntax.

  • To: mathgroup at smc.vnet.net
  • Subject: [mg104370] Re: problem of syntax.
  • From: David Bailey <dave at removedbailey.co.uk>
  • Date: Thu, 29 Oct 2009 02:58:07 -0500 (EST)
  • References: <hc91nu$e3r$1@smc.vnet.net>

micmac wrote:
> Hello everyone,
> 
> For some reasons, I have a matrix where each element is itself another
> matrix of size one.
> How can I transform that in a normal matrix where each element is just the
> value ?
> 
> I am very confused with mathematica syntax.
> 
> thanks,
> 
> Julien
> 
> 
> 
Given a nested list structure such as you describe, probably the easiest 
way to transform it is with Map:

In[6]:= start = {{{10}, {20}}, {{30}, {40}}};

In[13]:= Map[First, start, {2}]

Out[13]= {{10, 20}, {30, 40}}

Maybe the real question you need to ask is how you got that structure in 
the first place - you say "for some reasons". Tell us how you got there 
and we can fix your real problem!

Regarding Mathematica syntax, I would strongly recommend spending a few 
hours exploring the syntax before plunging into solving a specific 
problem of your own. Try the tutorials and/or type "lists" into the help 
system, and follow the various tutorial-style links such as 
"constructing lists". Remember that you can cut and paste the help 
examples into a notebook of your own. If you do this, you will quickly 
build up a collection of recipes to help you with your own work. 
Mathematica syntax is extremely logical and easy to use even if it 
appears hard at first - so persevere a bit. If all else fails, go on a 
short course.

David Bailey
http://www.dbaileyconsultancy.co.uk


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