R: Creates a unique integer key for unique combinations of rows...

ikey {ffbase} | R Documentation

## Creates a unique integer key for unique combinations of rows of an `ffdf`

### Description

Creates a unique integer key for unique combinations of rows of an `ffdf`. In database terms this would correspond to a primary or foreign key.
Orders the `ffdf` decreasingly alongside the columns with NA's as last in the order and creates the integer key.

### Usage

    ikey(x, ...)

### Arguments

`x` | an `ffdf`
`...` | other parameters passed on to chunk

### Value

An integer ff vector of the same length as the number of rows in `x` with unique values for each unique row

### Examples

    oldffmaxbytes <- getOption("ffmaxbytes")
    options(ffmaxbytes = 20)
    ffiris <- as.ffdf(iris)
    ffiris$key1 <- ikey(ffiris)
    ffiris$key2 <- ikey(ffiris[c("Petal.Width","Species")])
    unique(ffiris[c("key2","Petal.Width","Species")])[,]
    options(ffmaxbytes = oldffmaxbytes)

[Package ffbase version 0.13.1 Index]