is.sub.big.matrix {bigmemory}

Submatrix support

Description

This doesn't create a copy, it just provides a new version of the class which provides behavior for a contiguous submatrix of the big.matrix. Non-contiguous submatrices are not supported.

Usage

is.sub.big.matrix(x)

## S4 method for signature 'big.matrix'
is.sub.big.matrix(x)

sub.big.matrix(
  x,
  firstRow = 1,
  lastRow = NULL,
  firstCol = 1,
  lastCol = NULL,
  backingpath = NULL
)

## S4 method for signature 'big.matrix'
sub.big.matrix(
  x,
  firstRow = 1,
  lastRow = NULL,
  firstCol = 1,
  lastCol = NULL,
  backingpath = NULL
)

## S4 method for signature 'big.matrix.descriptor'
sub.big.matrix(
  x,
  firstRow = 1,
  lastRow = NULL,
  firstCol = 1,
  lastCol = NULL,
  backingpath = NULL
)

Arguments

x

A descriptor object

firstRow

the first row of the submatrix

lastRow

the last row of the submatrix if not NULL

firstCol

the first column of the submatrix

lastCol

of the submatrix if not NULL

backingpath

required path to the filebacked object, if applicable

Details

The sub.big.matrix function allows a user to create a big.matrix object that references a contiguous set of columns and rows of another big.matrix object.

The is.sub.big.matrix function returns TRUE if the specified argument is a sub.big.matrix object and return FALSE otherwise.

Value

A big.matrix which is actually a submatrix of a larger big.matrix. It is not a physical copy. Only contiguous blocks may form a submatrix.

Author(s)

John W. Emerson and Michael J. Kane

See Also

big.matrix

Examples

x <- big.matrix(10, 5, init=0, type="double")
x[,] <- 1:50
y <- sub.big.matrix(x, 2, 9, 2, 3)
y[,]
y[1,1] <- -99
x[,]
rm(x)