On Sun, Apr 6, 2008 at 10:38 PM, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> On Sun, 6 Apr 2008, Charles R Harris apparently wrote:
> > You mean as edges in a directed graph?
>
> Yes.
>
> Naturally a boolean matrix is not the most compact
> representation of a directed graph, especially a
> sparse o
On Sun, 6 Apr 2008, Charles R Harris apparently wrote:
> You mean as edges in a directed graph?
Yes.
Naturally a boolean matrix is not the most compact
representation of a directed graph, especially a
sparse one. However it can be convenient.
If B is a boolean matrix such that Bij=1 if there i
On Sun, Apr 6, 2008 at 8:51 PM, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> On Sun, 6 Apr 2008, Charles R Harris apparently wrote:
> > I prefer the modern usage myself as it is closer to the
> > accepted logic operations, but applying algebraic
> > manipulations like powers and matrix inverses in th
On Sun, 6 Apr 2008, Charles R Harris apparently wrote:
> I prefer the modern usage myself as it is closer to the
> accepted logic operations, but applying algebraic
> manipulations like powers and matrix inverses in that
> context leads to strange results.
I have not really thought much about
On Sun, 6 Apr 2008, Anne Archibald apparently wrote:
> I am not aware of any algorithm for finding inverses, or
> even determining which matrices are invertible, in the
> peculiar Boolean arithmetic we use.
Again, it is *not* peculiar, it is very standard for
boolean matrices. And with this be
> > and for negative powers some sort of floating-point
> > inverse.
>
> That deserves discussion.
> Not all "invertible" boolean matrices have an inverse in the algebra.
> Just the orthogonal ones do.
>
> I guess I would special case inverses for Boolean matrices.
> Just test if the matrix B
On Sun, Apr 6, 2008 at 2:34 PM, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> On Sun, 6 Apr 2008, Charles R Harris wrote:
> > The boolean algebra is a field and the correct addition is xor, which
> is
> > the same as addition modulo 2. This makes all matrices with determinant
> 1
> > invertible. This
On Sun, 6 Apr 2008, Charles R Harris wrote:
> The boolean algebra is a field and the correct addition is xor, which is
> the same as addition modulo 2. This makes all matrices with determinant 1
> invertible. This isn't the current convention, however, as it was when
> Caratheodory was writing
On Sun, Apr 6, 2008 at 12:59 PM, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> > On 06/04/2008, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> >> Just checking:
> >> it's important to me that this won't change
> >> the behavior of boolean matrices, but I don't
> >> see a test for this. E.g., ::
>
> >>
> On 06/04/2008, Alan G Isaac <[EMAIL PROTECTED]> wrote:
>> Just checking:
>> it's important to me that this won't change
>> the behavior of boolean matrices, but I don't
>> see a test for this. E.g., ::
>> >>> import numpy as N
>> >>> A = N.mat('1 0;1 1',dtype='bool')
>> >>> A**2
On 06/04/2008, Alan G Isaac <[EMAIL PROTECTED]> wrote:
> Just checking:
> it's important to me that this won't change
> the behavior of boolean matrices, but I don't
> see a test for this. E.g., ::
>
> >>> import numpy as N
> >>> A = N.mat('1 0;1 1',dtype='bool')
> >>> A**2
> m
On Sun, 6 Apr 2008, Stéfan van der Walt apparently wrote:
> I'd be glad if you would review the changeset and comment.
Just checking:
it's important to me that this won't change
the behavior of boolean matrices, but I don't
see a test for this. E.g., ::
>>> import numpy as N
>>> A = N.m
Hi all,
Some discussion recently took place around raising a square matrices
to integer powers. See ticket #601:
http://scipy.org/scipy/numpy/ticket/601
Anne Archibald wrote a patch which factored 'matrix_multiply' out of
defmatrix (the matrix power implemented for the Matrix class). After
som
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