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MathGroup Archive 2007

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Re: ReadList and columns

  • To: mathgroup at smc.vnet.net
  • Subject: [mg73922] Re: ReadList and columns
  • From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
  • Date: Sat, 3 Mar 2007 01:03:07 -0500 (EST)
  • Organization: The Open University, Milton Keynes, UK
  • References: <es91ti$3e5$1@smc.vnet.net>

Mary Beth Mulcahy wrote:

[...snip...]

> input:     au1[[All,{1}]]
> output:  {{350},{360},{370},{380},{390}}
> 
> input:     au1[[All,{2}]]
> output:   {{0.00023179},{0.0038609},{0.0075302},{0.008159},{0.0076243}}
> 
> And when I try and transpose the lists (Transpose[au1[[All,{1}]], au1[[All,
> {2}]]]) I get an error message saying the dimensions of my array are
> incorrect.
> 
> I know that I need Mathematica to read my columns like this:
> {350,360,370,380,390} without the extra curly brackets and which I believe
> would be a single array, but I can't figure out how to do it.  I would
> really appreciate any help.
> 
> Sincerely,
> Mary Beth Mulcahy
> 

Transpose first, then extract the desired column(s). For instance,

In[1]:=
au1 = {{350, 0.00023179}, {360, 0.0038609},
     {370, 0.0075302}, {380, 0.008159},
     {390, 0.0076243}};

In[2]:=
au1[[All,{1}]]

Out[2]=
{{350}, {360}, {370}, {380}, {390}}

In[3]:=
au1[[All,{2}]]

Out[3]=
{{0.00023179}, {0.0038609}, {0.0075302}, {0.008159},
   {0.0076243}}

In[4]:=
Transpose[au1][[1]]

Out[4]=
{350, 360, 370, 380, 390}

In[5]:=
Transpose[au1][[2]]

Out[5]=
{0.00023179, 0.0038609, 0.0075302, 0.008159, 0.0076243}

Regards,
Jean-Marc


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