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MathGroup Archive 2005

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Re: NewBie question Plot Table of points from a data file

  • To: mathgroup at smc.vnet.net
  • Subject: [mg53316] Re: [mg53270] NewBie question Plot Table of points from a data file
  • From: "David Annetts" <davidannetts at ihug.com.au>
  • Date: Wed, 5 Jan 2005 01:21:55 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

 
Hi jfj,

> I want to plot a file of data (x, y, z coordinate on each 
> line of an ascii file) I can read values with:
> pts = ReadList["myfile.dat", Table[Number, {3}]] but How 
> display it Show[Graphics3D[pts]] give me error How access to 
> my Table pts?

The following should get you started ...

pts = Table[{i, j, Random[Real, {-5, 5}]}, {i, 10}, {j, 10}];
pts = Partition[Flatten[pts], 3]
Show[Graphics3D[Point[#] & /@ pts],
    Axes -> True];

> How compute for instance pts[1,1] + pts[2,1] ?

Your syntax is wrong for starters, so it's difficult to know what you're
after.

In[26]:=
pts//Short
pts[[1, 1]]
pts[[2, 1]]
pts[[1, 1]] + pts[[2, 1]]

Out[26]//Short=
{{1,1,3.30002},{1,2,-0.172164},\[LeftSkeleton]97\[RightSkeleton],{10,10,1.\
63075}}

Out[27]=
1

Out[28]=
1

Out[29]=
2

Which might not be what you expected.  

I guess what you're after is the height, or last element of each point, in
which case
In[50]:=
Last@pts[[1]]
Last@pts[[2]]
Plus[
  Last@pts[[1]],
  Last@pts[[2]]]

Out[50]=
3.30002

Out[51]=
-0.172164

Out[52]=
3.12785

works.

For 5.0.1, Section 2.4.2 tells you all about parts of lists.

Regards,

Dave.

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