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 >