scipy.sparse.lil_matrix#
- class scipy.sparse.lil_matrix(arg1, shape=None, dtype=None, copy=False)[source]#
Row-based LIst of Lists sparse matrix.
This is a structure for constructing sparse matrices incrementally. Note that inserting a single item can take linear time in the worst case; to construct the matrix efficiently, make sure the items are pre-sorted by index, per row.
- This can be instantiated in several ways:
- lil_matrix(D)
where D is a 2-D ndarray
- lil_matrix(S)
with another sparse array or matrix S (equivalent to S.tolil())
- lil_matrix((M, N), [dtype])
to construct an empty matrix with 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.
- Advantages of the LIL format
supports flexible slicing
changes to the matrix sparsity structure are efficient
- Disadvantages of the LIL format
arithmetic operations LIL + LIL are slow (consider CSR or CSC)
slow column slicing (consider CSC)
slow matrix vector products (consider CSR or CSC)
- Intended Usage
LIL is a convenient format for constructing sparse matrices
once a matrix has been constructed, convert to CSR or CSC format for fast arithmetic and matrix vector operations
consider using the COO format when constructing large matrices
- Data Structure
An array (
self.rows
) of rows, each of which is a sorted list of column indices of non-zero elements.The corresponding nonzero values are stored in similar fashion in
self.data
.
- Attributes:
Methods
__len__
()__mul__
(other)asformat
(format[, copy])Return this array/matrix in the passed format.
asfptype
()Upcast matrix to a floating point format (if necessary)
astype
(dtype[, casting, copy])Cast the array/matrix elements to a specified type.
conj
([copy])Element-wise complex conjugation.
conjugate
([copy])Element-wise complex conjugation.
copy
()Returns a copy of this array/matrix.
Number of non-zero entries, equivalent to
diagonal
([k])Returns the kth diagonal of the array/matrix.
dot
(other)Ordinary dot product
getH
()Return the Hermitian transpose of this matrix.
Get the shape of the matrix
getcol
(j)Returns a copy of column j of the matrix, as an (m x 1) sparse matrix (column vector).
Matrix storage format
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) sparse matrix (row vector).
getrowview
(i)Returns a view of the 'i'th row (without copying).
maximum
(other)Element-wise maximum between this and another array/matrix.
mean
([axis, dtype, out])Compute the arithmetic mean along the specified axis.
minimum
(other)Element-wise minimum between this and another array/matrix.
multiply
(other)Point-wise multiplication by another array/matrix.
nonzero
()Nonzero indices of the array/matrix.
power
(n[, dtype])Element-wise power.
reshape
(self, shape[, order, copy])Gives a new shape to a sparse array/matrix without changing its data.
resize
(*shape)Resize the array/matrix in-place to dimensions given by
shape
set_shape
(shape)Set the shape of the matrix in-place
setdiag
(values[, k])Set diagonal or off-diagonal elements of the array/matrix.
sum
([axis, dtype, out])Sum the array/matrix elements over a given axis.
toarray
([order, out])Return a dense ndarray representation of this sparse array/matrix.
tobsr
([blocksize, copy])Convert this array/matrix to Block Sparse Row format.
tocoo
([copy])Convert this array/matrix to COOrdinate format.
tocsc
([copy])Convert this array/matrix to Compressed Sparse Column format.
tocsr
([copy])Convert this array/matrix to Compressed Sparse Row format.
todense
([order, out])Return a dense representation of this sparse array/matrix.
todia
([copy])Convert this array/matrix to sparse DIAgonal format.
todok
([copy])Convert this array/matrix to Dictionary Of Keys format.
tolil
([copy])Convert this array/matrix to List of Lists format.
trace
([offset])Returns the sum along diagonals of the sparse array/matrix.
transpose
([axes, copy])Reverses the dimensions of the sparse array/matrix.
__getitem__