scipy.sparse.csr_ matrix

Reference resources   https://cloud.tencent.com/developer/article/1525065

class scipy.sparse.csr_matrix(arg1, shape=None, dtype=None, copy=False)[source]

Compressed Sparse Row matrix

This can be instantiated in several ways:

csr_matrix(D)

with a dense matrix or rank-2 ndarray D

csr_matrix(S)

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

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

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

csr_matrix((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_matrix((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 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.

Advantages of the CSR format

    efficient arithmetic operations CSR + CSR, CSR * CSR, etc.
    efficient row slicing
    fast matrix 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_matrix
>>> csr_matrix((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_matrix((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_matrix((data, indices, indptr), shape=(3, 3)).toarray()
array([[1, 0, 2],
       [0, 0, 3],
       [4, 5, 6]])

As an example of how to construct a CSR matrix incrementally, the following snippet builds a term-document matrix 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_matrix((data, indices, indptr), dtype=int).toarray()
array([[2, 1, 0, 0],
       [0, 1, 1, 1]])

Attributes
nnz     Number of stored values, including explicit zeros.
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)
data         CSR format data array of the matrix
indices     CSR format index array of the matrix
indptr       CSR format index pointer array 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()     
count_nonzero()     Number of non-zero entries, equivalent to
deg2rad()     Element-wise deg2rad.
diagonal()     Returns the main 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()     
get_shape()     
getcol(i)     Returns a copy of column i of the matrix, as a (m x 1) CSR matrix (column vector).
getformat()     
getmaxprint()     
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)     
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)     
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(shape[, order])     Gives a new shape to a sparse matrix without changing its data.
rint()     Element-wise rint.
set_shape(shape)     
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])     See the docstring for spmatrix.toarray.
tobsr([blocksize, copy])     Convert this matrix to Block Sparse Row format.
tocoo([copy])     Convert this matrix to COOrdinate format.
tocsc([copy])     
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 LInked List format.
transpose([axes, copy])     Reverses the dimensions of the sparse matrix.
trunc()     Element-wise trunc.