Re: Simplify

• To: mathgroup at smc.vnet.net
• Subject: [mg91096] Re: Simplify
• From: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>
• Date: Wed, 6 Aug 2008 05:04:25 -0400 (EDT)
• Organization: The Open University, Milton Keynes, UK
• References: <g791is\$9ng\$1@smc.vnet.net>

```Cetin Haftaoglu wrote:

> I have a simple question about to simplify a expression (a list/matrices). I
> have a list like
>
> {2 cet1, 0, -2 cet1, cet1, 0, -cet1}
>
> And I want to extract if possible the factor cet1, so I become a list like
>
> cet1{2, 0, -2, 1, 0, -1}

Note that the above expression is *not* a list: This is the product of a
symbol by a list. Evaluating such an expression will result in the
original list (cet1 is distributed over the list).

> How can I extract the factor?

Among many other methods, you could use a transformation rule or a
function such as *Coefficient[]* (Note that the last expression uses the
non-commutative multiplication sign "**" to prevent distributivity):

In[1]:=
lst = {2 cet1, 0, -2 cet1, cet1, 0, -cet1}
lst /. cet1 -> 1
Coefficient[lst, cet1]
cet1 (lst /. cet1 -> 1)
cet1 ** (lst /. cet1 -> 1)

Out[1]= {2 cet1, 0, -2 cet1, cet1, 0, -cet1}

Out[2]= {2, 0, -2, 1, 0, -1}

Out[3]= {2, 0, -2, 1, 0, -1}

Out[4]= {2 cet1, 0, -2 cet1, cet1, 0, -cet1}

Out[5]= cet1 ** {2, 0, -2, 1, 0, -1}

Regards,
-- Jean-Marc

```

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