org.apache.spark.mllib.linalg.distributed

Class IndexedRowMatrix

Object

org.apache.spark.mllib.linalg.distributed.IndexedRowMatrix

All Implemented Interfaces:

java.io.Serializable, DistributedMatrix

public class IndexedRowMatrix
extends Object
implements DistributedMatrix

Represents a row-oriented DistributedMatrix with indexed rows.

param: rows indexed rows of this matrix param: nRows number of rows. A non-positive value means unknown, and then the number of rows will be determined by the max row index plus one. param: nCols number of columns. A non-positive value means unknown, and then the number of columns will be determined by the size of the first row.

See Also:

Serialized Form

Constructor Summary

Constructors

Constructor and Description
IndexedRowMatrix(RDD<IndexedRow> rows) Alternative constructor leaving matrix dimensions to be determined automatically.
IndexedRowMatrix(RDD<IndexedRow> rows, long nRows, int nCols)

Method Summary

Modifier and Type	Method and Description
CoordinateMatrix	columnSimilarities() Compute all cosine similarities between columns of this matrix using the brute-force approach of computing normalized dot products.
Matrix	computeGramianMatrix() Computes the Gramian matrix A^T A.
SingularValueDecomposition<IndexedRowMatrix,Matrix>	computeSVD(int k, boolean computeU, double rCond) Computes the singular value decomposition of this IndexedRowMatrix.
IndexedRowMatrix	multiply(Matrix B) Multiply this matrix by a local matrix on the right.
long	numCols() Gets or computes the number of columns.
long	numRows() Gets or computes the number of rows.
RDD<IndexedRow>	rows()
BlockMatrix	toBlockMatrix() Converts to BlockMatrix.
BlockMatrix	toBlockMatrix(int rowsPerBlock, int colsPerBlock) Converts to BlockMatrix.
CoordinateMatrix	toCoordinateMatrix() Converts this matrix to a CoordinateMatrix.
RowMatrix	toRowMatrix() Drops row indices and converts this matrix to a RowMatrix.

Methods inherited from class Object

equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

IndexedRowMatrix

public IndexedRowMatrix(RDD<IndexedRow> rows,
                        long nRows,
                        int nCols)

IndexedRowMatrix

public IndexedRowMatrix(RDD<IndexedRow> rows)

Alternative constructor leaving matrix dimensions to be determined automatically.

Method Detail

columnSimilarities

public CoordinateMatrix columnSimilarities()

Compute all cosine similarities between columns of this matrix using the brute-force approach of computing normalized dot products.

Returns:

An n x n sparse upper-triangular matrix of cosine similarities between columns of this matrix.

computeGramianMatrix

public Matrix computeGramianMatrix()

Computes the Gramian matrix A^T A.

Returns:

(undocumented)

Note:

This cannot be computed on matrices with more than 65535 columns.

computeSVD

public SingularValueDecomposition<IndexedRowMatrix,Matrix> computeSVD(int k,
                                                                      boolean computeU,
                                                                      double rCond)

Computes the singular value decomposition of this IndexedRowMatrix. Denote this matrix by A (m x n), this will compute matrices U, S, V such that A = U * S * V'.

The cost and implementation of this method is identical to that in RowMatrix With the addition of indices.

At most k largest non-zero singular values and associated vectors are returned. If there are k such values, then the dimensions of the return will be:

U is an IndexedRowMatrix of size m x k that satisfies U'U = eye(k), s is a Vector of size k, holding the singular values in descending order, and V is a local Matrix of size n x k that satisfies V'V = eye(k).

Parameters:

k - number of singular values to keep. We might return less than k if there are numerically zero singular values. See rCond.

computeU - whether to compute U

rCond - the reciprocal condition number. All singular values smaller than rCond * sigma(0) are treated as zero, where sigma(0) is the largest singular value.

Returns:

SingularValueDecomposition(U, s, V)

multiply

public IndexedRowMatrix multiply(Matrix B)

Multiply this matrix by a local matrix on the right.

Parameters:

B - a local matrix whose number of rows must match the number of columns of this matrix

Returns:

an IndexedRowMatrix representing the product, which preserves partitioning

numCols

public long numCols()

Description copied from interface: DistributedMatrix

Gets or computes the number of columns.

Specified by:

numCols in interface DistributedMatrix

numRows

public long numRows()

Description copied from interface: DistributedMatrix

Gets or computes the number of rows.

Specified by:

numRows in interface DistributedMatrix

rows

public RDD<IndexedRow> rows()

toBlockMatrix

public BlockMatrix toBlockMatrix()

Converts to BlockMatrix. Creates blocks with size 1024 x 1024.

Returns:

(undocumented)

toBlockMatrix

public BlockMatrix toBlockMatrix(int rowsPerBlock,
                                 int colsPerBlock)

Converts to BlockMatrix. Blocks may be sparse or dense depending on the sparsity of the rows.

Parameters:

rowsPerBlock - The number of rows of each block. The blocks at the bottom edge may have a smaller value. Must be an integer value greater than 0.

colsPerBlock - The number of columns of each block. The blocks at the right edge may have a smaller value. Must be an integer value greater than 0.

Returns:

a BlockMatrix

toCoordinateMatrix

public CoordinateMatrix toCoordinateMatrix()

Converts this matrix to a CoordinateMatrix.

Returns:

(undocumented)

toRowMatrix

public RowMatrix toRowMatrix()

Drops row indices and converts this matrix to a RowMatrix.

Returns:

(undocumented)