R: Getting and setting length

length.ff {ff} | R Documentation

## Getting and setting length

### Description

Gets and sets length of ff objects.

### Usage

    ## S3 method for class 'ff'
    length(x)
    ## S3 replacement method for class 'ff'
    length(x) <- value

### Arguments

`x` | object to query
`value` | new object length

### Details

Changing the length of ff objects is only allowed if no `vw` is used. Changing the length of ff objects will remove any `dim.ff` and `dimnames.ff` attribute. Changing the length of ff objects will remove any `na.count` or `is.sorted` attribute and warn about this. New elements are usually zero, but it may depend on OS and filesystem what they really are. If you want standard R behaviour: filling with NA ,you need to do this yourself. As an exception to this rule, ff objects with `names.ff` will be filled with NA's automatically, and the length of the names will be adjusted (filled with position numbers where needed, which can easily consume a lot of RAM, therefore removing 'names' will help to faster increase length without RAM problems).

### Value

Integer scalar

### Note

Special care needs to be taken with regard ff objects that represent factors. For ff factors based on UNSIGNED `vmodes`, new values of zero are silently interpreted as the first factor level. For ff factors based on SIGNED `vmodes`, new values of zero result in illegal factor levels. See `nrow<-`.

### Author(s)

Jens Oehlschlägel

### See Also

`length`, `maxlength`, `file.resize`, `dim`, `virtual`

### Examples

      x <- ff(1:12)
      maxlength(x)
      length(x)
      length(x) <- 10
      maxlength(x)
      length(x)
      length(x) <- 16
      maxlength(x)
      length(x)
      rm(x); gc()

[Package ff version 2.2-13 Index]