scipy.sparse.csr_array

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

Compressed Sparse Row array

This can be instantiated in several ways:

csr_array(D)

with a dense array or rank-2 ndarray D

csr_array(S)

with another sparse array S (equivalent to S.tocsr())

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

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

csr_array((data, (row_ind, col_ind)), [shape=(M, N)])

where data, row_ind and col_ind satisfy the relationship a[row_ind[k], col_ind[k]] = data[k].

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

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

Notes

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

Advantages of the CSR format

• efficient arithmetic operations CSR + CSR, CSR * CSR, etc.

• efficient row slicing

• fast array vector products

Disadvantages of the CSR format

• slow column slicing operations (consider CSC)

• changes to the sparsity structure are expensive (consider LIL or DOK)

Examples

>>> import numpy as np
>>> from scipy.sparse import csr_array
>>> csr_array((3, 4), dtype=np.int8).toarray()
array([[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])
>>> csr_array((data, (row, col)), shape=(3, 3)).toarray()
array([[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])
>>> csr_array((data, indices, indptr), shape=(3, 3)).toarray()
array([[1, 0, 2],
       [0, 0, 3],
       [4, 5, 6]])

Duplicate entries are summed together:

>>> row = np.array([0, 1, 2, 0])
>>> col = np.array([0, 1, 1, 0])
>>> data = np.array([1, 2, 4, 8])
>>> csr_array((data, (row, col)), shape=(3, 3)).toarray()
array([[9, 0, 0],
       [0, 2, 0],
       [0, 4, 0]])

As an example of how to construct a CSR array incrementally, the following snippet builds a term-document array from texts:

>>> docs = [["hello", "world", "hello"], ["goodbye", "cruel", "world"]]
>>> indptr = [0]
>>> indices = []
>>> data = []
>>> vocabulary = {}
>>> for d in docs:
...     for term in d:
...         index = vocabulary.setdefault(term, len(vocabulary))
...         indices.append(index)
...         data.append(1)
...     indptr.append(len(indices))
...
>>> csr_array((data, indices, indptr), dtype=int).toarray()
array([[2, 1, 0, 0],
       [0, 1, 1, 1]])

Attributes

dtypedtype

Data type of the array

shape2-tuple

Get shape of a matrix.

ndimint

Number of dimensions (this is always 2)

nnz

Number of stored values, including explicit zeros.

data

CSR format data array of the array

indices

CSR format index array of the array

indptr

CSR format index pointer array of the array

has_sorted_indices

Determine whether the matrix has sorted indices

Methods

__len__()
__mul__(*args, **kwargs)
arcsin()	Element-wise arcsin.
arcsinh()	Element-wise arcsinh.
arctan()	Element-wise arctan.
arctanh()	Element-wise arctanh.
argmax([axis, out])	Return indices of maximum elements along an axis.
argmin([axis, out])	Return indices of minimum elements along an axis.
asformat(format[, copy])	Return this matrix in the passed format.
asfptype()	Upcast matrix to a floating point format (if necessary)
astype(dtype[, casting, copy])	Cast the matrix elements to a specified type.
ceil()	Element-wise ceil.
check_format([full_check])	check whether the matrix format is valid
conj([copy])	Element-wise complex conjugation.
conjugate([copy])	Element-wise complex conjugation.
copy()	Returns a copy of this matrix.
count_nonzero()	Number of non-zero entries, equivalent to
deg2rad()	Element-wise deg2rad.
diagonal([k])	Returns the kth diagonal of the matrix.
dot(other)	Ordinary dot product
eliminate_zeros()	Remove zero entries from the matrix
expm1()	Element-wise expm1.
floor()	Element-wise floor.
getH()	Return the Hermitian transpose of this matrix.
get_shape()	Get shape of a matrix.
getcol(i)	Returns a copy of column i of the matrix, as a (m x 1) CSR matrix (column vector).
getformat()	Format of a matrix representation as a string.
getmaxprint()	Maximum number of elements to display when printed.
getnnz([axis])	Number of stored values, including explicit zeros.
getrow(i)	Returns a copy of row i of the matrix, as a (1 x n) CSR matrix (row vector).
log1p()	Element-wise log1p.
max([axis, out])	Return the maximum of the matrix or maximum along an axis.
maximum(other)	Element-wise maximum between this and another matrix.
mean([axis, dtype, out])	Compute the arithmetic mean along the specified axis.
min([axis, out])	Return the minimum of the matrix or maximum along an axis.
minimum(other)	Element-wise minimum between this and another matrix.
multiply(other)	Point-wise multiplication by another matrix, vector, or scalar.
nonzero()	nonzero indices
power(n[, dtype])	This function performs element-wise power.
prune()	Remove empty space after all non-zero elements.
rad2deg()	Element-wise rad2deg.
reshape(self, shape[, order, copy])	Gives a new shape to a sparse matrix without changing its data.
resize(*shape)	Resize the matrix in-place to dimensions given by shape
rint()	Element-wise rint.
set_shape(shape)	See reshape.
setdiag(values[, k])	Set diagonal or off-diagonal elements of the array.
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
sqrt()	Element-wise sqrt.
sum([axis, dtype, out])	Sum the matrix elements over a given axis.
sum_duplicates()	Eliminate duplicate matrix entries by adding them together
tan()	Element-wise tan.
tanh()	Element-wise tanh.
toarray([order, out])	Return a dense ndarray representation of this matrix.
tobsr([blocksize, copy])	Convert this matrix to Block Sparse Row format.
tocoo([copy])	Convert this matrix to COOrdinate format.
tocsc([copy])	Convert this matrix to Compressed Sparse Column format.
tocsr([copy])	Convert this matrix to Compressed Sparse Row format.
todense([order, out])	Return a dense matrix representation of this matrix.
todia([copy])	Convert this matrix to sparse DIAgonal format.
todok([copy])	Convert this matrix to Dictionary Of Keys format.
tolil([copy])	Convert this matrix to List of Lists format.
trace([offset])	Returns the sum along diagonals of the sparse matrix.
transpose([axes, copy])	Reverses the dimensions of the sparse matrix.
trunc()	Element-wise trunc.

__getitem__