Fixed database typo and removed unnecessary class identifier.

venv/Lib/site-packages/scipy/sparse/csc.py

@@ -0,0 +1,259 @@
+"""Compressed Sparse Column matrix format"""
+__docformat__ = "restructuredtext en"
+
+__all__ = ['csc_matrix', 'isspmatrix_csc']
+
+
+import numpy as np
+
+from .base import spmatrix
+from ._sparsetools import csc_tocsr, expandptr
+from .sputils import upcast, get_index_dtype
+
+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, (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]``.
+
+        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]: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.
+
+    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 stored values, including explicit zeros
+    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
+    --------
+
+    >>> import numpy as np
+    >>> from scipy.sparse import csc_matrix
+    >>> csc_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, 2, 2, 0, 1, 2])
+    >>> col = np.array([0, 0, 1, 2, 2, 2])
+    >>> data = np.array([1, 2, 3, 4, 5, 6])
+    >>> csc_matrix((data, (row, col)), shape=(3, 3)).toarray()
+    array([[1, 0, 4],
+           [0, 0, 5],
+           [2, 3, 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])
+    >>> csc_matrix((data, indices, indptr), shape=(3, 3)).toarray()
+    array([[1, 0, 4],
+           [0, 0, 5],
+           [2, 3, 6]])
+
+    """
+    format = 'csc'
+
+    def transpose(self, axes=None, copy=False):
+        if axes is not None:
+            raise ValueError(("Sparse matrices do not support "
+                              "an 'axes' parameter because swapping "
+                              "dimensions is the only logical permutation."))
+
+        M, N = self.shape
+
+        from .csr import csr_matrix
+        return csr_matrix((self.data, self.indices,
+                           self.indptr), (N, M), copy=copy)
+
+    transpose.__doc__ = spmatrix.transpose.__doc__
+
+    def __iter__(self):
+        for r in self.tocsr():
+            yield r
+
+    def tocsc(self, copy=False):
+        if copy:
+            return self.copy()
+        else:
+            return self
+
+    tocsc.__doc__ = spmatrix.tocsc.__doc__
+
+    def tocsr(self, copy=False):
+        M,N = self.shape
+        idx_dtype = get_index_dtype((self.indptr, self.indices),
+                                    maxval=max(self.nnz, N))
+        indptr = np.empty(M + 1, dtype=idx_dtype)
+        indices = np.empty(self.nnz, dtype=idx_dtype)
+        data = np.empty(self.nnz, dtype=upcast(self.dtype))
+
+        csc_tocsr(M, N,
+                  self.indptr.astype(idx_dtype),
+                  self.indices.astype(idx_dtype),
+                  self.data,
+                  indptr,
+                  indices,
+                  data)
+
+        from .csr import csr_matrix
+        A = csr_matrix((data, indices, indptr), shape=self.shape, copy=False)
+        A.has_sorted_indices = True
+        return A
+
+    tocsr.__doc__ = spmatrix.tocsr.__doc__
+
+    def nonzero(self):
+        # CSC can't use _cs_matrix's .nonzero method because it
+        # returns the indices sorted for self transposed.
+
+        # Get row and col indices, from _cs_matrix.tocoo
+        major_dim, minor_dim = self._swap(self.shape)
+        minor_indices = self.indices
+        major_indices = np.empty(len(minor_indices), dtype=self.indices.dtype)
+        expandptr(major_dim, self.indptr, major_indices)
+        row, col = self._swap((major_indices, minor_indices))
+
+        # Remove explicit zeros
+        nz_mask = self.data != 0
+        row = row[nz_mask]
+        col = col[nz_mask]
+
+        # Sort them to be in C-style order
+        ind = np.argsort(row, kind='mergesort')
+        row = row[ind]
+        col = col[ind]
+
+        return row, col
+
+    nonzero.__doc__ = _cs_matrix.nonzero.__doc__
+
+    def getrow(self, i):
+        """Returns a copy of row i of the matrix, as a (1 x n)
+        CSR matrix (row vector).
+        """
+        M, N = self.shape
+        i = int(i)
+        if i < 0:
+            i += M
+        if i < 0 or i >= M:
+            raise IndexError('index (%d) out of range' % i)
+        return self._get_submatrix(minor=i).tocsr()
+
+    def getcol(self, i):
+        """Returns a copy of column i of the matrix, as a (m x 1)
+        CSC matrix (column vector).
+        """
+        M, N = self.shape
+        i = int(i)
+        if i < 0:
+            i += N
+        if i < 0 or i >= N:
+            raise IndexError('index (%d) out of range' % i)
+        return self._get_submatrix(major=i, copy=True)
+
+    def _get_intXarray(self, row, col):
+        return self._major_index_fancy(col)._get_submatrix(minor=row)
+
+    def _get_intXslice(self, row, col):
+        if col.step in (1, None):
+            return self._get_submatrix(major=col, minor=row, copy=True)
+        return self._major_slice(col)._get_submatrix(minor=row)
+
+    def _get_sliceXint(self, row, col):
+        if row.step in (1, None):
+            return self._get_submatrix(major=col, minor=row, copy=True)
+        return self._get_submatrix(major=col)._minor_slice(row)
+
+    def _get_sliceXarray(self, row, col):
+        return self._major_index_fancy(col)._minor_slice(row)
+
+    def _get_arrayXint(self, row, col):
+        return self._get_submatrix(major=col)._minor_index_fancy(row)
+
+    def _get_arrayXslice(self, row, col):
+        return self._major_slice(col)._minor_index_fancy(row)
+
+    # 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]
+
+
+def isspmatrix_csc(x):
+    """Is x of csc_matrix type?
+
+    Parameters
+    ----------
+    x
+        object to check for being a csc matrix
+
+    Returns
+    -------
+    bool
+        True if x is a csc matrix, False otherwise
+
+    Examples
+    --------
+    >>> from scipy.sparse import csc_matrix, isspmatrix_csc
+    >>> isspmatrix_csc(csc_matrix([[5]]))
+    True
+
+    >>> from scipy.sparse import csc_matrix, csr_matrix, isspmatrix_csc
+    >>> isspmatrix_csc(csr_matrix([[5]]))
+    False
+    """
+    return isinstance(x, csc_matrix)