quantileCut: Cut by quantiles
In lsr: Companion to "Learning Statistics with R"

Description Usage Arguments Value See Also Examples

Cuts a variable into equal sized categories

It is sometimes convenient (though not always wise) to split a continuous numeric variable x into a set of n discrete categories that contain an approximately equal number of cases. The quantileCut function does exactly this. The actual categorisation is done by the cut function. However, instead of selecting ranges of equal sizes (the default behaviour in cut), the quantileCut function uses the quantile function to select unequal sized ranges so as to ensure that each of the categories contains the same number of observations. The intended purpose of the function is to assist in exploratory data analysis; it is not generally a good idea to use the output of quantileCut function as a factor in an analysis of variance, for instance, since the factor levels are not interpretable and will almost certainly violate homogeneity of variance.

1	quantileCut(x, n, ...)

`x`	A vector containing the observations.
`n`	Number of categories
`...`	Additional arguments to cut

A factor containing n levels. The factor levels are determined in the same way as for the cut function, and can be specified manually using the labels argument, which is passed to the cut function.

cut, quantile

# An example illustrating why care is needed

dataset <- c( 0,1,2, 3,4,5, 7,10,15 )       # note the uneven spread of data
x <- quantileCut( dataset, 3 )              # cut into 3 equally frequent bins
table(x)                                    # tabulate

# For comparison purposes, here is the behaviour of the more standard cut
# function when applied to the same data:
y <- cut( dataset, 3 )
table(y)