R: Function to group a variable in intervals.

ncut {Epi} | R Documentation

## Function to group a variable in intervals.

### Description

Cuts a continuous variable in intervals. As opposed to `cut` which returns a factor, `ncut` returns a numeric variable.

### Usage

    ncut(x, breaks, type="left" )

### Arguments

`x` | A numerical vector.
`breaks` | Vector of breakpoints. `NA` will results for values below `min(breaks)` if `type="left"`, for values above `max(breaks)` if `type="right"` and for values outside `range(breaks)` if `type="mid"`
`type` | Character: one of `c("left","right","mid")`, indicating whether the left, right or midpoint of the intervals defined in breaks is returned.

### Details

The function uses the base function `findInterval`.

### Value

A numerical vector of the same length as `x`.

### Author(s)

Bendix Carstensen, Steno Diabetes Center, b@bxc.dk, http://BendixCarstensen.com, with essential input from Martyn Plummer, IARC.

### See Also

`cut`, `findInterval`

### Examples

    br <- c(-2,0,1,2.5)
    x <- c( rnorm( 10 ), br, -3, 3 )
    cbind( x, l=ncut( x, breaks=br, type="l" ),
              m=ncut( x, breaks=br, type="m" ),
              r=ncut( x, breaks=br, type="r" ) )[order(x),]
    x <- rnorm( 200 )
    plot( x, ncut( x, breaks=br, type="l" ), pch=16, col="blue", ylim=range(x) )
    abline( 0, 1 )
    abline( v=br )
    points( x, ncut( x, breaks=br, type="r" ), pch=16, col="red" )
    points( x, ncut( x, breaks=br, type="m" ), pch=16, col="green" )

[Package Epi version 2.37 Index]