358 lines
11 KiB
Python
358 lines
11 KiB
Python
"""Compressed Sparse Row matrix format"""
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__docformat__ = "restructuredtext en"
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__all__ = ['csr_matrix', 'isspmatrix_csr']
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import numpy as np
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from .base import spmatrix
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from ._sparsetools import (csr_tocsc, csr_tobsr, csr_count_blocks,
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get_csr_submatrix)
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from .sputils import upcast, get_index_dtype
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from .compressed import _cs_matrix
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class csr_matrix(_cs_matrix):
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"""
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Compressed Sparse Row matrix
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This can be instantiated in several ways:
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csr_matrix(D)
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with a dense matrix or rank-2 ndarray D
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csr_matrix(S)
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with another sparse matrix S (equivalent to S.tocsr())
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csr_matrix((M, N), [dtype])
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to construct an empty matrix with shape (M, N)
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dtype is optional, defaulting to dtype='d'.
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csr_matrix((data, (row_ind, col_ind)), [shape=(M, N)])
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where ``data``, ``row_ind`` and ``col_ind`` satisfy the
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relationship ``a[row_ind[k], col_ind[k]] = data[k]``.
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csr_matrix((data, indices, indptr), [shape=(M, N)])
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is the standard CSR representation where the column indices for
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row i are stored in ``indices[indptr[i]:indptr[i+1]]`` and their
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corresponding values are stored in ``data[indptr[i]:indptr[i+1]]``.
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If the shape parameter is not supplied, the matrix dimensions
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are inferred from the index arrays.
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Attributes
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----------
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dtype : dtype
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Data type of the matrix
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shape : 2-tuple
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Shape of the matrix
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ndim : int
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Number of dimensions (this is always 2)
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nnz
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Number of stored values, including explicit zeros
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data
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CSR format data array of the matrix
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indices
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CSR format index array of the matrix
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indptr
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CSR format index pointer array of the matrix
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has_sorted_indices
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Whether indices are sorted
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Notes
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-----
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Sparse matrices can be used in arithmetic operations: they support
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addition, subtraction, multiplication, division, and matrix power.
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Advantages of the CSR format
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- efficient arithmetic operations CSR + CSR, CSR * CSR, etc.
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- efficient row slicing
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- fast matrix vector products
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Disadvantages of the CSR format
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- slow column slicing operations (consider CSC)
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- changes to the sparsity structure are expensive (consider LIL or DOK)
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Examples
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--------
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>>> import numpy as np
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>>> from scipy.sparse import csr_matrix
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>>> csr_matrix((3, 4), dtype=np.int8).toarray()
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array([[0, 0, 0, 0],
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[0, 0, 0, 0],
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[0, 0, 0, 0]], dtype=int8)
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>>> row = np.array([0, 0, 1, 2, 2, 2])
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>>> col = np.array([0, 2, 2, 0, 1, 2])
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>>> data = np.array([1, 2, 3, 4, 5, 6])
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>>> csr_matrix((data, (row, col)), shape=(3, 3)).toarray()
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array([[1, 0, 2],
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[0, 0, 3],
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[4, 5, 6]])
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>>> indptr = np.array([0, 2, 3, 6])
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>>> indices = np.array([0, 2, 2, 0, 1, 2])
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>>> data = np.array([1, 2, 3, 4, 5, 6])
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>>> csr_matrix((data, indices, indptr), shape=(3, 3)).toarray()
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array([[1, 0, 2],
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[0, 0, 3],
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[4, 5, 6]])
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Duplicate entries are summed together:
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>>> row = np.array([0, 1, 2, 0])
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>>> col = np.array([0, 1, 1, 0])
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>>> data = np.array([1, 2, 4, 8])
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>>> csr_matrix((data, (row, col)), shape=(3, 3)).toarray()
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array([[9, 0, 0],
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[0, 2, 0],
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[0, 4, 0]])
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As an example of how to construct a CSR matrix incrementally,
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the following snippet builds a term-document matrix from texts:
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>>> docs = [["hello", "world", "hello"], ["goodbye", "cruel", "world"]]
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>>> indptr = [0]
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>>> indices = []
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>>> data = []
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>>> vocabulary = {}
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>>> for d in docs:
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... for term in d:
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... index = vocabulary.setdefault(term, len(vocabulary))
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... indices.append(index)
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... data.append(1)
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... indptr.append(len(indices))
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...
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>>> csr_matrix((data, indices, indptr), dtype=int).toarray()
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array([[2, 1, 0, 0],
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[0, 1, 1, 1]])
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"""
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format = 'csr'
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def transpose(self, axes=None, copy=False):
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if axes is not None:
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raise ValueError(("Sparse matrices do not support "
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"an 'axes' parameter because swapping "
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"dimensions is the only logical permutation."))
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M, N = self.shape
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from .csc import csc_matrix
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return csc_matrix((self.data, self.indices,
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self.indptr), shape=(N, M), copy=copy)
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transpose.__doc__ = spmatrix.transpose.__doc__
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def tolil(self, copy=False):
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from .lil import lil_matrix
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lil = lil_matrix(self.shape,dtype=self.dtype)
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self.sum_duplicates()
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ptr,ind,dat = self.indptr,self.indices,self.data
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rows, data = lil.rows, lil.data
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for n in range(self.shape[0]):
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start = ptr[n]
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end = ptr[n+1]
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rows[n] = ind[start:end].tolist()
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data[n] = dat[start:end].tolist()
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return lil
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tolil.__doc__ = spmatrix.tolil.__doc__
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def tocsr(self, copy=False):
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if copy:
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return self.copy()
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else:
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return self
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tocsr.__doc__ = spmatrix.tocsr.__doc__
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def tocsc(self, copy=False):
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idx_dtype = get_index_dtype((self.indptr, self.indices),
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maxval=max(self.nnz, self.shape[0]))
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indptr = np.empty(self.shape[1] + 1, dtype=idx_dtype)
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indices = np.empty(self.nnz, dtype=idx_dtype)
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data = np.empty(self.nnz, dtype=upcast(self.dtype))
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csr_tocsc(self.shape[0], self.shape[1],
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self.indptr.astype(idx_dtype),
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self.indices.astype(idx_dtype),
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self.data,
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indptr,
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indices,
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data)
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from .csc import csc_matrix
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A = csc_matrix((data, indices, indptr), shape=self.shape)
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A.has_sorted_indices = True
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return A
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tocsc.__doc__ = spmatrix.tocsc.__doc__
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def tobsr(self, blocksize=None, copy=True):
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from .bsr import bsr_matrix
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if blocksize is None:
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from .spfuncs import estimate_blocksize
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return self.tobsr(blocksize=estimate_blocksize(self))
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elif blocksize == (1,1):
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arg1 = (self.data.reshape(-1,1,1),self.indices,self.indptr)
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return bsr_matrix(arg1, shape=self.shape, copy=copy)
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else:
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R,C = blocksize
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M,N = self.shape
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if R < 1 or C < 1 or M % R != 0 or N % C != 0:
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raise ValueError('invalid blocksize %s' % blocksize)
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blks = csr_count_blocks(M,N,R,C,self.indptr,self.indices)
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idx_dtype = get_index_dtype((self.indptr, self.indices),
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maxval=max(N//C, blks))
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indptr = np.empty(M//R+1, dtype=idx_dtype)
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indices = np.empty(blks, dtype=idx_dtype)
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data = np.zeros((blks,R,C), dtype=self.dtype)
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csr_tobsr(M, N, R, C,
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self.indptr.astype(idx_dtype),
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self.indices.astype(idx_dtype),
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self.data,
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indptr, indices, data.ravel())
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return bsr_matrix((data,indices,indptr), shape=self.shape)
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tobsr.__doc__ = spmatrix.tobsr.__doc__
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# these functions are used by the parent class (_cs_matrix)
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# to remove redudancy between csc_matrix and csr_matrix
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def _swap(self, x):
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"""swap the members of x if this is a column-oriented matrix
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"""
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return x
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def __iter__(self):
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indptr = np.zeros(2, dtype=self.indptr.dtype)
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shape = (1, self.shape[1])
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i0 = 0
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for i1 in self.indptr[1:]:
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indptr[1] = i1 - i0
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indices = self.indices[i0:i1]
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data = self.data[i0:i1]
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yield csr_matrix((data, indices, indptr), shape=shape, copy=True)
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i0 = i1
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def getrow(self, i):
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"""Returns a copy of row i of the matrix, as a (1 x n)
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CSR matrix (row vector).
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"""
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M, N = self.shape
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i = int(i)
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if i < 0:
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i += M
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if i < 0 or i >= M:
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raise IndexError('index (%d) out of range' % i)
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indptr, indices, data = get_csr_submatrix(
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M, N, self.indptr, self.indices, self.data, i, i + 1, 0, N)
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return csr_matrix((data, indices, indptr), shape=(1, N),
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dtype=self.dtype, copy=False)
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def getcol(self, i):
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"""Returns a copy of column i of the matrix, as a (m x 1)
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CSR matrix (column vector).
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"""
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M, N = self.shape
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i = int(i)
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if i < 0:
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i += N
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if i < 0 or i >= N:
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raise IndexError('index (%d) out of range' % i)
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indptr, indices, data = get_csr_submatrix(
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M, N, self.indptr, self.indices, self.data, 0, M, i, i + 1)
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return csr_matrix((data, indices, indptr), shape=(M, 1),
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dtype=self.dtype, copy=False)
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def _get_intXarray(self, row, col):
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return self.getrow(row)._minor_index_fancy(col)
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def _get_intXslice(self, row, col):
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if col.step in (1, None):
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return self._get_submatrix(row, col, copy=True)
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# TODO: uncomment this once it's faster:
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# return self.getrow(row)._minor_slice(col)
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M, N = self.shape
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start, stop, stride = col.indices(N)
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ii, jj = self.indptr[row:row+2]
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row_indices = self.indices[ii:jj]
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row_data = self.data[ii:jj]
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if stride > 0:
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ind = (row_indices >= start) & (row_indices < stop)
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else:
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ind = (row_indices <= start) & (row_indices > stop)
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if abs(stride) > 1:
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ind &= (row_indices - start) % stride == 0
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row_indices = (row_indices[ind] - start) // stride
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row_data = row_data[ind]
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row_indptr = np.array([0, len(row_indices)])
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if stride < 0:
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row_data = row_data[::-1]
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row_indices = abs(row_indices[::-1])
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shape = (1, int(np.ceil(float(stop - start) / stride)))
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return csr_matrix((row_data, row_indices, row_indptr), shape=shape,
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dtype=self.dtype, copy=False)
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def _get_sliceXint(self, row, col):
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if row.step in (1, None):
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return self._get_submatrix(row, col, copy=True)
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return self._major_slice(row)._get_submatrix(minor=col)
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def _get_sliceXarray(self, row, col):
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return self._major_slice(row)._minor_index_fancy(col)
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def _get_arrayXint(self, row, col):
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return self._major_index_fancy(row)._get_submatrix(minor=col)
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def _get_arrayXslice(self, row, col):
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if col.step not in (1, None):
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col = np.arange(*col.indices(self.shape[1]))
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return self._get_arrayXarray(row, col)
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return self._major_index_fancy(row)._get_submatrix(minor=col)
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def isspmatrix_csr(x):
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"""Is x of csr_matrix type?
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Parameters
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----------
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x
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object to check for being a csr matrix
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Returns
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-------
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bool
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True if x is a csr matrix, False otherwise
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Examples
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--------
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>>> from scipy.sparse import csr_matrix, isspmatrix_csr
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>>> isspmatrix_csr(csr_matrix([[5]]))
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True
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>>> from scipy.sparse import csc_matrix, csr_matrix, isspmatrix_csc
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>>> isspmatrix_csr(csc_matrix([[5]]))
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False
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"""
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return isinstance(x, csr_matrix)
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