R: Cut a Numeric Variable to a Factor

cutfac {vcdExtra} | R Documentation

## Cut a Numeric Variable to a Factor

### Description

`cutfac` acts like `cut`, dividing the range of `x` into intervals and coding the values in `x` according in which interval they fall. However, it gives nicer labels for the factor levels and by default chooses convenient breaks among the values based on deciles.

It is particularly useful for plots in which one wants to make a numeric variable discrete for the purpose of getting boxplots, spinograms or mosaic plots.

### Usage

    cutfac(x, breaks = NULL, q = 10)

### Arguments

`x` | a numeric vector which is to be converted to a factor by cutting
`breaks` | either a numeric vector of two or more unique cut points or a single number (greater than or equal to 2) giving the number of intervals into which `x` is to be cut.
`q` | the number of quantile groups used to define `breaks`, if that has not been specified.

### Details

By default, `cut` chooses breaks by equal lengths of the range of `x`, whereas `cutfac` uses `quantile` to choose breaks of roughly equal count.

### Value

A `factor` corresponding to `x` is returned

### Author(s)

Achim Zeileis

### References

Friendly, M. and Meyer, D. (2016). Discrete Data Analysis with R: Visualization and Modeling Techniques for Categorical and Count Data. Boca Raton, FL: Chapman & Hall/CRC. http://ddar.datavis.ca.

### See Also

`cut`, `quantile`

### Examples

    if (require(AER)) {
    data("NMES1988", package="AER")
    nmes <- NMES1988[, c(1, 6:8, 13, 15, 18)]

    plot(log(visits+1) ~ cutfac(chronic), data = nmes,
      ylab = "Physician office visits (log scale)",
      xlab = "Number of chronic conditions", main = "chronic")

    plot(log(visits+1) ~ cutfac(hospital, c(0:2, 8)), data = nmes,
      ylab = "Physician office visits (log scale)",
      xlab = "Number of hospital stays", main = "hospital")
    }

[Package vcdExtra version 0.7-1 Index]