``` >>> BlockMatrix([[eye(2),2*eye(2)],[3*eye(2),4*eye(2)]]).as_explicit() Matrix([ [1, 0, 2, 0], [0, 1, 0, 2], [3, 0, 4, 0], [0, 3, 0, 4]]) ``` See also #16454 <https://github.com/sympy/sympy/pull/16454>
On Thursday, November 8, 2018 at 1:40:49 AM UTC-6, Aaron Meurer wrote: > > I think a fromblocks classmethod would be useful. > > Also I don't see why BlockMatrix shouldn't automatically flatten when > all the entries are explicit matrices. Or at the least have a method > that does so. > > As for Matrix([[eye(2), eye(2)], [eye(2), eye(2)]]), it seems it > should either auto-flatten, or create a BlockMatrix. > > Aaron Meurer > On Wed, Nov 7, 2018 at 4:56 PM Oscar Benjamin > <oscar.j....@gmail.com <javascript:>> wrote: > > > > Is there a straight-forward way to create a matrix from blocks? > > > > The Matrix.diag function is nice for creating a block diagonal matrix: > > > > In [1]: Matrix.diag(2*eye(2),3*eye(3)) > > Out[1]: > > ⎡2 0 0 0 0⎤ > > ⎢ ⎥ > > ⎢0 2 0 0 0⎥ > > ⎢ ⎥ > > ⎢0 0 3 0 0⎥ > > ⎢ ⎥ > > ⎢0 0 0 3 0⎥ > > ⎢ ⎥ > > ⎣0 0 0 0 3⎦ > > > > I'd like to do something similar but for a general block matrix. I > > imagine something like: > > > > >>> Matrix.fromblocks([[eye(2),2*eye(2)],[3*eye(2),4*eye(2)]]) > > > > The expected output would be: > > > > [1 0 2 0] > > [0 1 0 2] > > [3 0 4 0] > > [0 3 0 4] > > > > This almost works if I pass a list of matrices to the Matrix > constructor: > > > > In [5]: Matrix([eye(2), eye(2)]) > > Out[5]: > > ⎡1 0⎤ > > ⎢ ⎥ > > ⎢0 1⎥ > > ⎢ ⎥ > > ⎢1 0⎥ > > ⎢ ⎥ > > ⎣0 1⎦ > > > > It doesn't work if I try to concatenate horizontally though: > > > > In [7]: Matrix([[eye(2), eye(2)]]) > > Out[7]: > > ⎡⎡1 0⎤ ⎡1 0⎤⎤ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎣⎣0 1⎦ ⎣0 1⎦⎦ > > > > Same happens if I try to do both: > > > > In [8]: Matrix([[eye(2), eye(2)], [eye(2), eye(2)]]) > > Out[8]: > > ⎡⎡1 0⎤ ⎡1 0⎤⎤ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎢⎣0 1⎦ ⎣0 1⎦⎥ > > ⎢ ⎥ > > ⎢⎡1 0⎤ ⎡1 0⎤⎥ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎣⎣0 1⎦ ⎣0 1⎦⎦ > > > > I see that there is a BlockMatrix class but I don't want a block > > matrix. I want to construct a normal matrix from blocks (similar to > > diag). There is a deblock function but it doesn't do what I hoped: > > > > In [13]: from sympy.matrices.expressions.blockmatrix import deblock > > > > In [14]: deblock(Matrix([[eye(2), eye(2)], [eye(2), eye(2)]])) > > Out[14]: > > ⎡⎡1 0⎤ ⎡1 0⎤⎤ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎢⎣0 1⎦ ⎣0 1⎦⎥ > > ⎢ ⎥ > > ⎢⎡1 0⎤ ⎡1 0⎤⎥ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎣⎣0 1⎦ ⎣0 1⎦ > > > > In [15]: deblock(BlockMatrix([[eye(2), eye(2)], [eye(2), eye(2)]])) > > Out[15]: > > ⎡⎡1 0⎤ ⎡1 0⎤⎤ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎢⎣0 1⎦ ⎣0 1⎦⎥ > > ⎢ ⎥ > > ⎢⎡1 0⎤ ⎡1 0⎤⎥ > > ⎢⎢ ⎥ ⎢ ⎥⎥ > > ⎣⎣0 1⎦ ⎣0 1⎦⎦ > > > > Am I missing a similar way to do this? > > > > -- > > Oscar > > > > -- > > You received this message because you are subscribed to the Google > Groups "sympy" group. > > To unsubscribe from this group and stop receiving emails from it, send > an email to sympy+un...@googlegroups.com <javascript:>. > > To post to this group, send email to sy...@googlegroups.com > <javascript:>. > > Visit this group at https://groups.google.com/group/sympy. > > To view this discussion on the web visit > https://groups.google.com/d/msgid/sympy/CAHVvXxTUe8Qtu1YGzcKWtR7Q_SXfOrenxqYORE_i6hCS8VnMuA%40mail.gmail.com. > > > > For more options, visit https://groups.google.com/d/optout. > -- You received this message because you are subscribed to the Google Groups "sympy" group. To unsubscribe from this group and stop receiving emails from it, send an email to sympy+unsubscr...@googlegroups.com. To post to this group, send email to sympy@googlegroups.com. Visit this group at https://groups.google.com/group/sympy. To view this discussion on the web visit https://groups.google.com/d/msgid/sympy/5fd0d4ec-3843-400e-92ca-a840bb283ffb%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
