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MathGroup Archive 1999

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Re: Table extraction

  • To: mathgroup at smc.vnet.net
  • Subject: [mg19236] Re: Table extraction
  • From: "Lars Hohmuth" <larsh at wolfram.com>
  • Date: Wed, 11 Aug 1999 02:06:50 -0400
  • Organization: Wolfram Research, Inc.
  • References: <7odkbs$7mq@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

If you happen to be using Mathematica 4, you can use All to select columns.

In[7]:=
tab1 = {{a, b, c}, {d, e, f}, {g, h, i}};
In[8]:=
tab1[[All, 1]]  (*selects the first column*)
Out[8]=
{a, d, g}
In[9]:=
tab1[[1]] == tab1[[1, All]] (*[[1]] and [[1,All]] both select the first
row*)
Out[9]=
True
In[10]:=
tab1[[{1, 2}, {1, 2}]] (*selecting a submatrix*)
Out[10]=
{{a, b}, {d, e}}
In[11]:=
tab1[[{1, 3}, {2, 3}]] (*selecting elements 2 and 3 of rows 1 and 3*)

Out[11]=
{{b, c}, {h, i}}

Lars Hohmuth
Wolfram Research, Inc.

Maurice Shevalier <maurice at phas.ucalgary.ca> wrote in message
news:7odkbs$7mq at smc.vnet.net...
> Hi,
>
> I am trying to extract a section of a table with not much luck....
>
> I have defined two tables (actually two arrays which are used to plot
> vectors with ListPlotVectorField) as follows:
>
> xyvector = Table[{0.,0.},{j,1,64},{i,1,320}];
> backvector = Table[{0.,0.},{j,1,16},{i,1,100}];
>
> I need to extract part of xyvector and place it into  backvector. I have
> tried to use Part. I can extract the j range correctly (rows), but I
> can't get the Part function to extract in the i range (columns).
>
> I tried using Part[xyvector,{2,3}] which extracts 2 rows but I cannot
> figute out how to extract the necessary columns
>
> Can anyone help?
>
> Thanks,
>
> Maurice
>
> --
> Maurice Shevalier                 |       .~.
> Ph.D. Candidate                   |       /V\       L   I   N   U   X
> Dept. of Physics and Astronomy    |      // \\  >The Penguin, The Slayer?<
> University of Calgary             |     /(   )\
> Calgary, AB, CANADA T2N-1N4       |      ^^-^^
> (403)220-7873   fax:(403)284-0074 |
> e-mail: maurice at phas.ucalgary.ca
>
>
>
>




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