Re: Manipulating List Elements In Programs

• To: mathgroup at smc.vnet.net
• Subject: [mg23968] Re: Manipulating List Elements In Programs
• From: "Atul Sharma" <atulksharma at yahoo.com>
• Date: Sun, 18 Jun 2000 03:00:50 -0400 (EDT)
• Organization: McGill University
• References: <8icdhn\$9sk@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```When you use Delete this way, you haven't actually redefined your list z. As
in this example, z hasn't been changed.

In
z= {a, b, c, d};
Delete[z, 3]
z

Out
{a, b, d}
{a, b, c, d}

What you really want to do is redefine the list, as in

In
z=Delete[z,3]
z

Out
{a, b, d}
{a, b, d}

In you case, you may also find z=Rest[z] a convenient way to trim element 1
from the list.

Atul

-------------------------------------------------------------------------
Atul Sharma MD, FRCP(C)
Pediatric Nephrologist,
McGill University/Montreal Children's Hospital

Buz Barstow wrote in message <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?
>