scipy.sparse.bsr_matrix

class scipy.sparse.bsr_matrix(arg1, shape=None, dtype=None, copy=False, blocksize=None)

Block Sparse Row matrix

This can be instantiated in several ways:

bsr_matrix(D, [blocksize=(R,C)])

with a dense matrix or rank-2 ndarray D

bsr_matrix(S, [blocksize=(R,C)])

with another sparse matrix S (equivalent to S.tobsr())

bsr_matrix((M, N), [blocksize=(R,C), dtype])

to construct an empty matrix with shape (M, N) dtype is optional, defaulting to dtype=’d’.

bsr_matrix((data, ij), [blocksize=(R,C), shape=(M, N)])

where data and ij satisfy a[ij[0, k], ij[1, k]] = data[k]

bsr_matrix((data, indices, indptr), [shape=(M, N)])

is the standard BSR representation where the block column indices for row i are stored in indices[indptr[i]:indptr[i+1]] and their corresponding block values are stored in data[ indptr[i]: indptr[i+1] ]. If the shape parameter is not supplied, the matrix dimensions are inferred from the index arrays.

Notes

Sparse matrices can be used in arithmetic operations: they support addition, subtraction, multiplication, division, and matrix power.

Summary of BSR format

The Block Compressed Row (BSR) format is very similar to the Compressed Sparse Row (CSR) format. BSR is appropriate for sparse matrices with dense sub matrices like the last example below. Block matrices often arise in vector-valued finite element discretizations. In such cases, BSR is considerably more efficient than CSR and CSC for many sparse arithmetic operations.

Blocksize

The blocksize (R,C) must evenly divide the shape of the matrix (M,N). That is, R and C must satisfy the relationship M % R = 0 and N % C = 0.

If no blocksize is specified, a simple heuristic is applied to determine an appropriate blocksize.

Examples

>>> from scipy.sparse import bsr_matrix
>>> bsr_matrix((3,4), dtype=np.int8).todense()
matrix([[0, 0, 0, 0],
        [0, 0, 0, 0],
        [0, 0, 0, 0]], dtype=int8)

>>> row = np.array([0,0,1,2,2,2])
>>> col = np.array([0,2,2,0,1,2])
>>> data = np.array([1,2,3,4,5,6])
>>> bsr_matrix((data, (row,col)), shape=(3,3)).todense()
matrix([[1, 0, 2],
        [0, 0, 3],
        [4, 5, 6]])

>>> indptr = np.array([0,2,3,6])
>>> indices = np.array([0,2,2,0,1,2])
>>> data = np.array([1,2,3,4,5,6]).repeat(4).reshape(6,2,2)
>>> bsr_matrix((data,indices,indptr), shape=(6,6)).todense()
matrix([[1, 1, 0, 0, 2, 2],
        [1, 1, 0, 0, 2, 2],
        [0, 0, 0, 0, 3, 3],
        [0, 0, 0, 0, 3, 3],
        [4, 4, 5, 5, 6, 6],
        [4, 4, 5, 5, 6, 6]])

Attributes

has_sorted_indices

Determine whether the matrix has sorted indices

dtype	(dtype) Data type of the matrix
shape	(2-tuple) Shape of the matrix
ndim	(int) Number of dimensions (this is always 2)
nnz	Number of nonzero elements
data	Data array of the matrix
indices	BSR format index array
indptr	BSR format index pointer array
blocksize	Block size of the matrix

Methods

arcsin()	Element-wise arcsin.
arcsinh()	Element-wise arcsinh.
arctan()	Element-wise arctan.
arctanh()	Element-wise arctanh.
asformat(format)	Return this matrix in a given sparse format
asfptype()	Upcast matrix to a floating point format (if necessary)
astype(t)
ceil()	Element-wise ceil.
check_format([full_check])	check whether the matrix format is valid
conj()
conjugate()
copy()
deg2rad()	Element-wise deg2rad.
diagonal()	Returns the main diagonal of the matrix
dot(other)
eliminate_zeros()
expm1()	Element-wise expm1.
floor()	Element-wise floor.
getH()
get_shape()
getcol(j)	Returns a copy of column j of the matrix, as an (m x 1) sparse
getdata(ind)
getformat()
getmaxprint()
getnnz()
getrow(i)	Returns a copy of row i of the matrix, as a (1 x n) sparse
log1p()	Element-wise log1p.
matmat(other)
matvec(other)
mean([axis])	Average the matrix over the given axis.
multiply(other)	Point-wise multiplication by another matrix
nonzero()	nonzero indices
prune()	Remove empty space after all non-zero elements.
rad2deg()	Element-wise rad2deg.
reshape(shape)
rint()	Element-wise rint.
set_shape(shape)
setdiag(values[, k])	Fills the diagonal elements {a_ii} with the values from the given sequence.
sign()	Element-wise sign.
sin()	Element-wise sin.
sinh()	Element-wise sinh.
sort_indices()	Sort the indices of this matrix in place
sorted_indices()	Return a copy of this matrix with sorted indices
sum([axis])	Sum the matrix over the given axis.
sum_duplicates()
tan()	Element-wise tan.
tanh()	Element-wise tanh.
toarray([order, out])	See the docstring for spmatrix.toarray.
tobsr([blocksize, copy])
tocoo([copy])	Convert this matrix to COOrdinate format.
tocsc()
tocsr()
todense([order, out])	Return a dense matrix representation of this matrix.
todia()
todok()
tolil()
transpose()
trunc()	Element-wise trunc.