Re: Manipulating List Elements In Programs

*To*: mathgroup at smc.vnet.net*Subject*: [mg23962] Re: Manipulating List Elements In Programs*From*: "Allan Hayes" <hay at haystack.demon.co.uk>*Date*: Sun, 18 Jun 2000 03:00:45 -0400 (EDT)*References*: <8icdhn$9sk@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Buz, The trouble may be in the use of Delete 1) Delete[z,{1,2}] needs to be Delete[z,{{1},{2}] 2) Delete[z,{{1},{2}] does not alter the value of z, it simplygives as output the value of z with the first two elements deleted. The following might work files = FileNames["output*.dat"]; l = Length[files]; For[i = 1, i <= l, i++, z = Import[ files[[i]]]; title = z[[1]]; lab = z[[2]]; lst = Delete[z, {{1}, {2}}]; ListPlot[lst, AxesLabel -> lab, PlotLabel -> title] ] A more functional form is ListPlot[Drop[#, 2], PlotLabel -> #[[1]], AxesLabel -> #[[2]]] &[Import[#] ] &/@ FileNames["output*.dat"] -- 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 "Buz Barstow" <buz at sys-j25.demon.co.uk> wrote in message news:8icdhn$9sk at smc.vnet.net... > Hi, > > I'm trying to write a program in Mathematica to automatically plot graphs > from text files that I've generated with a C program. It looks in the > working directory, and retrieves a list of all files with a .dat extension; > > files = FileNames["output*.dat"] > > Then, it gets the number of entries in that list; > > l = Length[files] > > And then uses this information to import each file individually and do a > ListPlot with each list; > > For[i = 1, i <= l, i++, > z = Import[ files[[i]]]; > title = z[[1]]; > lab = z[[2]]; > Delete[z, {1, 2}]; > ListPlot[z, AxesLabel -> lab, PlotLabel -> title] ] > > At the top of each output file there is a heading that I want to use as the > plot's title and two column headings that I want to use to label the axes. > Unfortunately, I can retrieve them and label the plot, but I can't delete > them, so when I include the title, I can't produce the plot. > > Does Mathematica prevent the programming calls deleting things, or am I > missing something? > > Thanks in advance, > > Buz > >