Re: list

• To: mathgroup at smc.vnet.net
• Subject: [mg3970] Re: list
• From: ianc (Ian Collier)
• Date: Mon, 13 May 1996 01:47:37 -0400
• Organization: Wolfram Research, Inc.
• Sender: owner-wri-mathgroup at wolfram.com

```In article <4lse5f\$hjq at dragonfly.wolfram.com>, Ahmad Khalid
<khalid at ciril.fr> wrote:

> i just start with mathematica.. i just want to know how can we modifie a list
> of list in mathematica. (ex { {1,2,3},{3,4,5},{5,6,7}})
> thank you

If you simply want to replace elements in your list here
are two ways:

In[7]:=
mylist = { {1,2,3},{3,4,5},{5,6,7}}
Out[7]=
{{1, 2, 3}, {3, 4, 5}, {5, 6, 7}}

In[8]:=
?ReplacePart

ReplacePart[expr, new, n] yields an expression in which the
nth part of expr is replaced by new. ReplacePart[expr,
new, {i, j, ...}] replaces the part at position {i, j,
...}. ReplacePart[expr, new, {{i1, j1, ...}, {i2, j2,
...}, ...}] replaces parts at several positions by new.

In[9]:=
mylist = ReplacePart[ mylist, a^2, {1,2}]
Out[9]=
2
{{1, a , 3}, {3, 4, 5}, {5, 6, 7}}

In[10]:=
mylist
Out[10]=
2
{{1, a , 3}, {3, 4, 5}, {5, 6, 7}}

In[11]:=
mylist[[2,2]] = c
Out[11]=
c

In[12]:=
mylist
Out[12]=
2
{{1, a , 3}, {3, c, 5}, {5, 6, 7}}

You can also add and remove elements. For further details see
section 1.8.6 of the Mathematica book, "Adding, Removing and
Modifying List Elements.

If you require further help with this I would suggest that you
contact Wolfram Research Technical Support (support at wolfram.com)
directly including specific details of what you are trying to do.

I hope this helps.

--Ian

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