Get ramclass and ramattribs

Functions ramclass and ramattribs return the respective virtual attributes, that determine which class (and attributes) an ff object receives when subscripted (or coerced) to ram.

ramclass(x, ...)
# S3 method for class 'ff'
ramclass(x, ...)
# Default S3 method
ramclass(x, ...)
ramattribs(x, ...)
# S3 method for class 'ff'
ramattribs(x, ...)
# Default S3 method
ramattribs(x, ...)

Arguments

x

x

...

further arguments (not used)

Details

ramclass and ramattribs provide a general mechanism to store atomic classes in ff objects, for example factor – see levels.ff – and POSIXct, see the example.

Value

ramclass returns a character vector with classnames and ramattribs returns a list with names elemens just like attributes. The vectors ramclass_excludes and ramattribs_excludes name those attributes, which are not exported from ff to ram objects when using as.ram.

Author

Jens Oehlschlägel

Examples

  x <- ff(as.POSIXct(as.POSIXlt(Sys.time(), "GMT")), length=12)
  x
#> ff (open) double length=12 (12)
#>                       [1]                       [2]                       [3] 
#> 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 
#>                       [4]                       [5]                       [6] 
#> 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 
#>                                                 [7]                       [8] 
#>                         : 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 
#>                       [9]                      [10]                      [11] 
#> 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 2025-03-17 22:35:54.24404 
#>                      [12] 
#> 2025-03-17 22:35:54.24404 
  ramclass(x)
#> [1] "POSIXct" "POSIXt" 
  ramattribs(x)
#> $tzone
#> [1] "GMT"
#> 
  class(x[])
#> [1] "POSIXct" "POSIXt" 
  attributes(x[])
#> $tzone
#> [1] "GMT"
#> 
#> $class
#> [1] "POSIXct" "POSIXt" 
#> 
  virtual(x)$ramattribs$tzone = NULL
  attributes(x[])
#> $class
#> [1] "POSIXct" "POSIXt" 
#> 
  rm(x); gc()
#>           used (Mb) gc trigger  (Mb) max used  (Mb)
#> Ncells 1162681 62.1    1994352 106.6  1994352 106.6
#> Vcells 2167203 16.6    8790397  67.1  8790397  67.1