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"""Compressed Sparse Column matrix format"""
__docformat__ = "restructuredtext en"
__all__ = ['csc_matrix', 'isspmatrix_csc']
from warnings import warn
import numpy as np
from sparsetools import csc_tocsr
from sputils import upcast, isintlike
from compressed import _cs_matrix
class csc_matrix(_cs_matrix):
"""
Compressed Sparse Column matrix
This can be instantiated in several ways:
csc_matrix(D)
with a dense matrix or rank-2 ndarray D
csc_matrix(S)
with another sparse matrix S (equivalent to S.tocsc())
csc_matrix((M, N), [dtype])
to construct an empty matrix with shape (M, N)
dtype is optional, defaulting to dtype='d'.
csc_matrix((data, ij), [shape=(M, N)])
where ``data`` and ``ij`` satisfy the relationship
``a[ij[0, k], ij[1, k]] = data[k]``
csc_matrix((data, indices, indptr), [shape=(M, N)])
is the standard CSC representation where the row indices for
column i are stored in ``indices[indptr[i]:indices[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.
Attributes
----------
dtype : dtype
Data type of the matrix
shape : 2-tuple
Shape of the matrix
ndim : int
Number of dimensions (this is always 2)
nnz
Number of nonzero elements
data
Data array of the matrix
indices
CSC format index array
indptr
CSC format index pointer array
has_sorted_indices
Whether indices are sorted
Notes
-----
Sparse matrices can be used in arithmetic operations: they support
addition, subtraction, multiplication, division, and matrix power.
Advantages of the CSC format
- efficient arithmetic operations CSC + CSC, CSC * CSC, etc.
- efficient column slicing
- fast matrix vector products (CSR, BSR may be faster)
Disadvantages of the CSC format
- slow row slicing operations (consider CSR)
- changes to the sparsity structure are expensive (consider LIL or DOK)
Examples
--------
>>> from scipy.sparse import *
>>> from scipy import *
>>> csc_matrix( (3,4), dtype=int8 ).todense()
matrix([[0, 0, 0, 0],
[0, 0, 0, 0],
[0, 0, 0, 0]], dtype=int8)
>>> row = array([0,2,2,0,1,2])
>>> col = array([0,0,1,2,2,2])
>>> data = array([1,2,3,4,5,6])
>>> csc_matrix( (data,(row,col)), shape=(3,3) ).todense()
matrix([[1, 0, 4],
[0, 0, 5],
[2, 3, 6]])
>>> indptr = array([0,2,3,6])
>>> indices = array([0,2,2,0,1,2])
>>> data = array([1,2,3,4,5,6])
>>> csc_matrix( (data,indices,indptr), shape=(3,3) ).todense()
matrix([[1, 0, 4],
[0, 0, 5],
[2, 3, 6]])
"""
def transpose(self, copy=False):
from csr import csr_matrix
M,N = self.shape
return csr_matrix((self.data,self.indices,self.indptr),(N,M),copy=copy)
def __iter__(self):
csr = self.tocsr()
for r in xrange(self.shape[0]):
yield csr[r,:]
def tocsc(self, copy=False):
if copy:
return self.copy()
else:
return self
def tocsr(self):
M,N = self.shape
indptr = np.empty(M + 1, dtype=np.intc)
indices = np.empty(self.nnz, dtype=np.intc)
data = np.empty(self.nnz, dtype=upcast(self.dtype))
csc_tocsr(M, N, \
self.indptr, self.indices, self.data, \
indptr, indices, data)
from csr import csr_matrix
A = csr_matrix((data, indices, indptr), shape=self.shape)
A.has_sorted_indices = True
return A
def __getitem__(self, key):
# use CSR to implement fancy indexing
if isinstance(key, tuple):
row = key[0]
col = key[1]
if isintlike(row) or isinstance(row, slice):
return self.T[col,row].T
else:
#[[1,2],??] or [[[1],[2]],??]
if isintlike(col) or isinstance(col,slice):
return self.T[col,row].T
else:
row = np.asarray(row, dtype=np.intc)
col = np.asarray(col, dtype=np.intc)
if len(row.shape) == 1:
return self.T[col,row]
elif len(row.shape) == 2:
row = row.reshape(-1)
col = col.reshape(-1,1)
return self.T[col,row].T
else:
raise NotImplementedError('unsupported indexing')
return self.T[col,row].T
elif isintlike(key) or isinstance(key,slice):
return self.T[:,key].T #[i] or [1:2]
else:
return self.T[:,key].T #[[1,2]]
# these functions are used by the parent class (_cs_matrix)
# to remove redudancy between csc_matrix and csr_matrix
def _swap(self,x):
"""swap the members of x if this is a column-oriented matrix
"""
return (x[1],x[0])
from sputils import _isinstance
def isspmatrix_csc(x):
return _isinstance(x, csc_matrix)
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