On Jan 8, 2008 11:05 PM, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote:
>
>
>
> On Jan 9, 7:43 am, "William Stein" <[EMAIL PROTECTED]> wrote:
>
> > On Jan 8, 2008 4:27 AM, vgermrk <[EMAIL PROTECTED]> wrote:
> >
> >
> >
> > > Is there a way to construct block matrices in SAGE?
> > > Not just the "block_sum", "augment" and "stack" functions.
> >
> > > As an example, let A, B, C, D be matrices and i want to construct a
> > > matrix like E=[[A,B],[C,D]]
> >
> > > Such a feature would be very nice.
> >
> > Sage's MatrixSpace and matrix don't have support for this.
> > numpy (which you get via "import numpy") might have support
> > for numerical matrices like this.
>
> CVXOPT also has support for this:
> http://abel.ee.ucla.edu/cvxopt/examples/short-examples/creating-matrices/
And, just to be clear, CVXOPT is standard in Sage.
There are a number of caveats though. Currently you really have to switch
to python mode to create a cvxopt matrix in Sage, probably because of
preparser issues (see below). Also, more importantly, it looks to me
like making a matrix from matrices in CVXOPT does *not* make a matrix
with matrix entries, but instead makes a single matrix -- see below.
{{{id=0|
%python
from cvxopt.base import matrix
A = matrix([1.0, 2.0, 3.0, 4.0, 5.0, 6.0], (2,3))
print A
///
1.0000e+00 3.0000e+00 5.0000e+00
2.0000e+00 4.0000e+00 6.0000e+00
}}}
{{{id=1|
%python
B = matrix([ [1.0, 2.0], [3.0, 4.0] ])
print B
///
1.0000e+00 3.0000e+00
2.0000e+00 4.0000e+00
}}}
{{{id=2|
%python
a = matrix([ [A] ,[B] ])
}}}
{{{id=4|
print a
///
1.0000e+00 3.0000e+00 5.0000e+00 1.0000e+00 3.0000e+00
2.0000e+00 4.0000e+00 6.0000e+00 2.0000e+00 4.0000e+00
}}}
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