R: Submatrix support

is.sub.big.matrix {bigmemory} | R Documentation

## 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
    )

### Arguments

`x` | either a `big.matrix` or a descriptor.
`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` | the last column 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)

[Package bigmemory version 4.5.36 Index]