Re: Help on Function

• To: mathgroup at smc.vnet.net
• Subject: [mg3849] Re: Help on Function
• From: ianc (Ian Collier)
• Date: Mon, 29 Apr 1996 00:33:34 -0400
• Organization: Wolfram Research, Inc.
• Sender: owner-wri-mathgroup at wolfram.com

```In article <4lesps\$e4m at dragonfly.wolfram.com>, Roberto Diego
<roberto at medusa.es> wrote:

> Hi people,
>
> if possible) that works on a list such as {a1, a2, a3, a4, ...} and
> returns a list {a2/a1, a3/a2, a4/a3, ...}. I know it should be an easy
> task but I4m a newbe...
>
> Thanks a lot

You can use Partition (with an offset of 1 specified as the third argument)
to divide your list up and then Map a suitable function across the list of
pairs.

The following should do what you want:

In[16]:=
ls = {a1, a2, a3, a4, a5, a6}
Out[16]=
{a1, a2, a3, a4, a5, a6}

In[17]:=
f[ list_ ] := Map[ #[[2]]/#[[1]] &, Partition[ list, 2, 1 ]]

In[18]:=
f[ls]
Out[18]=
a2  a3  a4  a5  a6
{--, --, --, --, --}
a1  a2  a3  a4  a5

I hope this helps.

--Ian

-----------------------------------------------------------
Ian Collier
Wolfram Research, Inc.
-----------------------------------------------------------
tel:(217) 398-0700   fax:(217) 398-0747    ianc at wolfram.com