Re: Merge of Matrices

• To: mathgroup at smc.vnet.net
• Subject: [mg71152] Re: Merge of Matrices
• From: "astanoff" <astanoff at gmail.com>
• Date: Thu, 9 Nov 2006 03:38:56 -0500 (EST)
• References: <eisglr\$nf9\$1@smc.vnet.net>

```On 8 nov, 12:56, Robert Berger <rberge... at sinh.us> wrote:
> Hello!
>
> I like to create from the four matrices A (N1 rows and N1 columns),
> B (N1 rows and N2 columns), C (N2 rows and N1 columns),
> D (N2 rows and N2 columns) a new matrix X of the form
>
>       A  B
> X =
>       C  D
>
> Once A & B and C & D have been merged, the first (A & B) and the
> second row (C& D) can be merged in that way by applying Join, which is
> not a problem but how can I merge A & B (and of course C & D) in
> that way?
>
> Kindly regards,
> Roman.

Example :

In[1]:=n1=2; n2=3;

In[2]:=aa=Array[a,{n1,n1}]; bb=Array[b,{n1,n2}];

In[3]:=cc=Array[c,{n2,n1}]; dd=Array[d,{n2,n2}];

In[4]:=x=Array[0&,{n1+n2,n1+n2}];

In[5]:=x[[Range[1,n1],Range[1,n1]]] = aa;
x[[Range[1,n1],Range[n1+1,n1+n2]]] = bb;
x[[Range[n1+1,n1+n2],Range[1,n1]]] = cc;
x[[Range[n1+1,n1+n2],Range[n1+1,n1+n2]]] = dd;

In[9]:=x

Out[9]={
{a[1,1],a[1,2],b[1,1],b[1,2],b[1,3]},
{a[2,1],a[2,2],b[2,1],b[2,2],b[2,3]},
{c[1,1],c[1,2],d[1,1],d[1,2],d[1,3]},
{c[2,1],c[2,2],d[2,1],d[2,2],d[2,3]},
{c[3,1],c[3,2],d[3,1],d[3,2],d[3,3]}}

hth

V.Astanoff

```

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