generate matrix from submatrices.
- Subject: generate matrix from submatrices.
- From: Rupert Swarbrick
- Date: Tue, 14 Dec 2010 09:10:02 +0000
Moch Ramis <mocramis at gmail.com> writes:
> Hello
>
> I'm probably asking something really basic, but I've not been able to have
> it working: I'm trying to create a 9x9 matrix from 1x3 matrix:
> something like:
> [ A 0 0 ]
> [ 0 A 0 ]
> [ 0 0 A ]
> [ B 0 0 ]
> M= [ 0 B 0 ]
> [ 0 0 B ]
> [ C 0 0 ]
> [ 0 C 0 ]
> [ 0 0 C ]
>
> where A,B,C ar some 1x3 matrices.
>
How about the following?
make_row(lst) := block([ret: []],
for x in lst do ret: append(ret, x), ret)$
make_diag_block(triple) :=
matrix(
make_row([triple, [0,0,0], [0,0,0]]),
make_row([[0,0,0], triple, [0,0,0]]),
make_row([[0,0,0], [0,0,0], triple]))$
make_stripes(A,B,C) :=
addrow(make_diag_block(A), make_diag_block(B), make_diag_block(C))$
giving:
(%i27) make_stripes([1,2,3], [2,3,4], [3,4,5]);
[ 1 2 3 0 0 0 0 0 0 ]
[ ]
[ 0 0 0 1 2 3 0 0 0 ]
[ ]
[ 0 0 0 0 0 0 1 2 3 ]
[ ]
[ 2 3 4 0 0 0 0 0 0 ]
[ ]
(%o27) [ 0 0 0 2 3 4 0 0 0 ]
[ ]
[ 0 0 0 0 0 0 2 3 4 ]
[ ]
[ 3 4 5 0 0 0 0 0 0 ]
[ ]
[ 0 0 0 3 4 5 0 0 0 ]
[ ]
[ 0 0 0 0 0 0 3 4 5 ]
(%i28)
There might be an easier/more efficient way to do it, but I'm not sure
how.
Rupert
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