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Re: Help on Function


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

> Hi people,
> 
> Could you please help me? I4m trying to write a function (not procedure 
> 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

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