scipy.sparse.lil_matrix

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

Row-based linked list sparse matrix

This is an efficient structure for constructing sparse matrices incrementally.

This can be instantiated in several ways:
lil_matrix(D)
with a dense matrix or rank-2 ndarray D
lil_matrix(S)
with another sparse matrix S (equivalent to S.tocsc())
lil_matrix((M, N), [dtype])
to construct an empty matrix with shape (M, N) dtype is optional, defaulting to dtype=’d’.

Notes

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.

Methods

asformat(format) Return this matrix in a given sparse format
asfptype() Upcast matrix to a floating point format (if necessary)
astype(t)
conj()
conjugate()
copy()
diagonal() Returns the main diagonal of the matrix
dot(other)
getH()
get_shape()
getcol(j) Returns a copy of column j of the matrix, as an (m x 1) sparse
getformat()
getmaxprint()
getnnz()
getrow(i) Returns a copy of the ‘i’th row.
getrowview(i) Returns a view of the ‘i’th row (without copying).
mean([axis]) Average the matrix over the given axis.
multiply(other) Point-wise multiplication by another matrix
nonzero() nonzero indices
reshape(shape)
set_shape(shape)
setdiag(values[, k]) Fills the diagonal elements {a_ii} with the values from the given sequence.
sum([axis]) Sum the matrix over the given axis.
toarray()
tobsr([blocksize])
tocoo()
tocsc() Return Compressed Sparse Column format arrays for this matrix.
tocsr() Return Compressed Sparse Row format arrays for this matrix.
todense()
todia()
todok()
tolil([copy])
transpose()

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