R: Create a Factor Variable Using the Quantiles of a Continuous...

quantcut {gtools} | R Documentation

## Create a Factor Variable Using the Quantiles of a Continuous Variable

### Description

Create a factor variable using the quantiles of a continous variable.

### Usage

    quantcut(x, q=4, na.rm=TRUE, ...)

### Arguments

`x` | Continous variable.
`q` | Either a integer number of equally spaced quantile groups to create, or a vector of quantiles used for creating groups. Defaults to `q=4` which is equivalent to `q=seq(0, 1, by=0.25)`. See `quantile` for details.
`na.rm` | Boolean indicating whether missing values should be removed when computing quantiles. Defaults to TRUE.
`...` | Optional arguments passed to `cut`.

### Details

This function uses `quantile` to obtain the specified quantiles of `x`, then calls `cut` to create a factor variable using the intervals specified by these quantiles.

It properly handles cases where more than one quantile obtains the same value, as in the second example below. Note that in this case, there will be fewer generated factor levels than the specified number of quantile intervals.

### Value

Factor variable with one level for each quantile interval.

### Author(s)

Gregory R. Warnes greg@warnes.net

### See Also

`cut`, `quantile`

### Examples

      ## create example data

      x <- rnorm(1000)

      ## cut into quartiles
      quartiles <- quantcut( x )
      table(quartiles)

      ## cut into deciles
      deciles.1 <- quantcut( x, 10 )
      table(deciles.1)
      # or equivalently
      deciles.2 <- quantcut( x, seq(0,1,by=0.1) )

      ## show handling of 'tied' quantiles.
      x <- round(x)  # discretize to create ties
      stem(x)        # display the ties
      deciles <- quantcut( x, 10 )

      table(deciles) # note that there are only 5 groups (not 10)
                     # due to duplicates

[Package gtools version 3.5.0 Index]