R: Getting and setting 'na.count' physical attribute

na.count {ff} | R Documentation

## Getting and setting 'na.count' physical attribute

### Description

The 'na.count' physical attribute gives the current number of NAs if properly initialized and properly maintained, see details.

### Usage

    ## S3 method for class 'ff'
    na.count(x, ...)
    ## Default S3 method:
    na.count(x, ...)
    ## S3 replacement method for class 'ff'
    na.count(x, ...) <- value
    ## Default S3 replacement method:
    na.count(x, ...) <- value

### Arguments

`x` | an ff or ram object
`...` | further arguments (not used)
`value` | NULL (to remove the 'na.count' attribute) or TRUE to activate or an integer value

### Details

The 'na.count' feature is activated by assigning the current number of NAs to `na.count(x) <- currentNA` and deactivated by assigning NULL. The 'na.count' feature is maintained by the, `getset.ff`, `readwrite.ff` and `swap`, other ff methods for writing – `set.ff`, `[[<-.ff`, `write.ff`, `[<-.ff` – will stop if 'na.count' is activated. The functions `na.count` and `na.count<-` are generic. For ram objects, the default method for `na.count` calculates the number of NAs on the fly, thus no maintenance restrictions apply.

### Value

NA (if set to NULL or NA) or an integer value otherwise

### Author(s)

Jens Oehlschlägel, Daniel Adler (C++ back-end)

### See Also

`getset.ff`, `readwrite.ff` and `swap` for methods that support maintenance of 'na.count', `NA`, `is.sorted` for yet another `physical` attribute

### Examples

      message("--- ff examples ---")
      x <- ff(1:12)
      na.count(x)
      message("activate the 'na.count' physical attribute and set the current na.count manually")
      na.count(x) <- 0L
      message("add one NA with a method that maintains na.count")
      swap(x, NA, 1)
      na.count(x)
      message("remove the 'na.count' physical attribute (and stop automatic maintenance)")
      na.count(x) <- NULL
      message("activate the 'na.count' physical attribute and have ff automatically
    calculate the current na.count")
      na.count(x) <- TRUE
      na.count(x)
      message("--- ram examples ---")
      x <- 1:12
      na.count(x)
      x[1] <- NA
      message("activate the 'na.count' physical attribute and have R automatically
    calculate the current na.count")
      na.count(x) <- TRUE
      na.count(x)
      message("remove the 'na.count' physical attribute (and stop automatic maintenance)")
      na.count(x) <- NULL
      na.count(x)
      rm(x); gc()

[Package ff version 2.2-13 Index]