scipy.sparse.dok_matrix

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

Dictionary Of Keys based sparse matrix.

This is an efficient structure for constructing sparse matrices incrementally.

This can be instantiated in several ways:

dok_matrix(D)

with a dense matrix, D

dok_matrix(S)

with a sparse matrix, S

dok_matrix((M,N), [dtype])

create the matrix with initial shape (M,N) dtype is optional, defaulting to dtype=’d’

Notes

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

Allows for efficient O(1) access of individual elements. Duplicates are not allowed. Can be efficiently converted to a coo_matrix once constructed.

Examples

>>> import numpy as np
>>> from scipy.sparse import dok_matrix
>>> S = dok_matrix((5, 5), dtype=np.float32)
>>> for i in range(5):
...     for j in range(5):
...         S[i, j] = i + j    # Update element

Attributes:

dtype : dtype

Data type of the matrix

shape : 2-tuple

Get shape of a matrix.

ndim : int

Number of dimensions (this is always 2)

nnz

Number of stored values, including explicit zeros.

Methods

asformat(self, format[, copy])	Return this matrix in the passed format.
asfptype(self)	Upcast matrix to a floating point format (if necessary)
astype(self, dtype[, casting, copy])	Cast the matrix elements to a specified type.
clear()
conj(self[, copy])	Element-wise complex conjugation.
conjtransp(self)	Return the conjugate transpose.
conjugate(self[, copy])	Element-wise complex conjugation.
copy(self)	Returns a copy of this matrix.
count_nonzero(self)	Number of non-zero entries, equivalent to
diagonal(self[, k])	Returns the k-th diagonal of the matrix.
dot(self, other)	Ordinary dot product
fromkeys()	v defaults to None.
get(self, key[, default])	This overrides the dict.get method, providing type checking but otherwise equivalent functionality.
getH(self)	Return the Hermitian transpose of this matrix.
get_shape(self)	Get shape of a matrix.
getcol(self, j)	Returns the j-th column as a (m x 1) DOK matrix.
getformat(self)	Format of a matrix representation as a string.
getmaxprint(self)	Maximum number of elements to display when printed.
getnnz(self[, axis])	Number of stored values, including explicit zeros.
getrow(self, i)	Returns the i-th row as a (1 x n) DOK matrix.
has_key()
items()
iteritems()
iterkeys()
itervalues()
keys()
maximum(self, other)	Element-wise maximum between this and another matrix.
mean(self[, axis, dtype, out])	Compute the arithmetic mean along the specified axis.
minimum(self, other)	Element-wise minimum between this and another matrix.
multiply(self, other)	Point-wise multiplication by another matrix
nonzero(self)	nonzero indices
pop()	If key is not found, d is returned if given, otherwise KeyError is raised
popitem()	2-tuple; but raise KeyError if D is empty.
power(self, n[, dtype])	Element-wise power.
reshape(self, shape[, order, copy])	Gives a new shape to a sparse matrix without changing its data.
resize(self, \*shape)	Resize the matrix in-place to dimensions given by shape
setdefault()
setdiag(self, values[, k])	Set diagonal or off-diagonal elements of the array.
sum(self[, axis, dtype, out])	Sum the matrix elements over a given axis.
toarray(self[, order, out])	Return a dense ndarray representation of this matrix.
tobsr(self[, blocksize, copy])	Convert this matrix to Block Sparse Row format.
tocoo(self[, copy])	Convert this matrix to COOrdinate format.
tocsc(self[, copy])	Convert this matrix to Compressed Sparse Column format.
tocsr(self[, copy])	Convert this matrix to Compressed Sparse Row format.
todense(self[, order, out])	Return a dense matrix representation of this matrix.
todia(self[, copy])	Convert this matrix to sparse DIAgonal format.
todok(self[, copy])	Convert this matrix to Dictionary Of Keys format.
tolil(self[, copy])	Convert this matrix to LInked List format.
transpose(self[, axes, copy])	Reverses the dimensions of the sparse matrix.
values()
viewitems()
viewkeys()
viewvalues()

set_shape
update