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 |

`obj` |
an object as returned by |

`...` |
possibly |

### 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[,]
```

*bigmemory*version 4.6.4 Index]