R: The basic "big.matrix" operations for sharing and...

describe,big.matrix-method {bigmemory} | R Documentation

## The basic “big.matrix” operations for sharing and re-attaching.

### Description

The `describe` function returns the information needed by `attach.big.matrix` to reference a shared or file-backed `big.matrix` object. The `attach.big.matrix` and `attach.resource` functions create a new `big.matrix` object based on the descriptor information referencing previously allocated shared-memory or file-backed matrices.

### Usage

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

    attach.big.matrix(obj, ...)

### Arguments

`x` | a `big.matrix` object
`obj` | an object as returned by `describe()` or, optionally, the filename of the descriptor for a filebacked matrix, assumed to be in the directory specified by the `path` (if one is provided)
`...` | possibly `path` which gives the path where the descriptor and/or filebacking can be found

### Details

The `describe` function returns a list of the information needed to attach to a `big.matrix` object. A descriptor file is automatically created when a new filebacked `big.matrix` is created.

### Value

`describe` returns a list of of the information needed to attach to a `big.matrix` object.

`attach.big.matrix` return a new instance of type `big.matrix` corresponding to a shared-memory or file-backed `big.matrix`.

### Author(s)

Michael J. Kane and John W. Emerson <bigmemoryauthors@gmail.com>

### See Also

`bigmemory`, `big.matrix`, or the class documentation `big.matrix`.

### Examples

    # The example is quite silly, as you wouldn't likely do this in a
    # single R session.  But if zdescription were passed to another R session
    # via SNOW, foreach, or even by a simple file read/write,
    # then the attach of the second R process would give access to the
    # same object in memory.  Please see the package vignette for real examples.

    z <- big.matrix(3, 3, type='integer', init=3)
    z[,]
    dim(z)
    z[1,1] <- 2
    z[,]
    zdescription <- describe(z)
    zdescription
    y <- attach.big.matrix(zdescription)
    y[,]
    y
    z
    zz <- attach.resource(zdescription)
    zz[1,1] <- -100
    y[,]
    z[,]

[Package bigmemory version 4.5.36 Index]