gtools (version 3.9.5)

quantcut: Create a Factor Variable Using the Quantiles of a Continuous Variable

Description

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

Usage

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

Value

Factor variable with one level for each quantile interval.

Arguments

x

Continuous 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.

Author

Gregory R. Warnes

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.

See Also

cut, quantile

Examples

## create example data
# testonly{
set.seed(1234)
# }
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))

# testonly{
stopifnot(identical(deciles.1, deciles.2))
# }

## 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