
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 ff
ramclass(x, …)
# S3 method for default
ramclass(x, …)
ramattribs(x, …)
# S3 method for ff
ramattribs(x, …)
# S3 method for default
ramattribs(x, …)
x
further arguments (not used)
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
.
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.
# NOT RUN {
x <- ff(as.POSIXct(as.POSIXlt(Sys.time(), "GMT")), length=12)
x
ramclass(x)
ramattribs(x)
class(x[])
attributes(x[])
virtual(x)$ramattribs$tzone = NULL
attributes(x[])
rm(x); gc()
# }
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