Re: Nested Lists
- To: mathgroup at smc.vnet.net
- Subject: [mg28399] Re: Nested Lists
- From: "Allan Hayes" <hay at haystack.demon.co.uk>
- Date: Mon, 16 Apr 2001 03:28:50 -0400 (EDT)
- References: <9b8ol0$7et@smc.vnet.net>
- Sender: owner-wri-mathgroup at wolfram.com
Robert,
I have taken N = 2 below, and changed N to NN, since N is protected.
NN=2;
With your reading method
ReadList["temp.txt",{Number,Table[Number,{NN},{3}]}]
{{1,{{2,3,4},{5,6,7}}},{2,{{3,4,5},{6,7,8}}}}
We can proceed:
(Flatten[#,1]&/@dat1)[[All,{1,3}]]
{{1,{5,6,7}},{2,{6,7,8}}}
Changing the reading method slightly
ReadList["temp.txt",Prepend[ Table[Number,{NN},{3}],Number]]
{{1,{2,3,4},{5,6,7}},{2,{3,4,5},{6,7,8}}}
allows us to use the simpler
%[[All,{1,3}]]
{{1,{5,6,7}},{2,{6,7,8}}}
--
Allan
---------------------
Allan Hayes
Mathematica Training and Consulting
Leicester UK
www.haystack.demon.co.uk
hay at haystack.demon.co.uk
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565
"Robert Love" <rlove at neosoft.com> wrote in message
news:9b8ol0$7et at smc.vnet.net...
> I'm confused about nested lists and how to select/extract data from them.
>
> I have a file of data I can use ReadList to read. The data is laid out
> like this:
>
> t1
> x y z
> x y z
> x y z
> x y z
> t2
> x y z
> x y z
> x y z
> x y z
> t3
> etc.
>
> The data consists of a timestamp on a line and then the 3D position of
> each of the N objects for that time. N is always the same number
> so I read it it like this:
>
> ReadList["file",{Number, Table[Number, Number, Number,{N}]}]
>
> I'm doing this from memory since the computer w/Mathematica is at work.
> So I may not have every detail of the ReadList correct but what I end up
> with is
>
> {{t1,{{x,y,z},{x,y,z},{x,y,z},{x,y,z}},
> {t2,{{x,y,z}...
>
>
> My question is now do I extract this suitable for graphing, that is, how
> do I turn this into something like a set of all the object #4 positions
> along with the time? I'm sure there is some combination of Flatten, Take,
> Transpose and Map that will do what I want. What is it? Also, is there
> a better way to use ReadList? I'm stuck with the file format but I can
> change how I read the data.
>
> All advice appreciated.
>
> Bob Love
>