quantile.numeric: Sample Quantiles

In USGS-R/smwrStats: R functions to support statistical methods in water resources

Sample Quantiles

Description

Computes sample quantiles corresponding to the given probabilities: method for "numeric" data. The smallest observation corresponds to a probability of 0 and the largest to a probability of 1. This method function is a simple wrapper for the default function that sets the default type to 2 for numeric data.

Usage

## S3 method for class 'numeric'
quantile(x, probs = seq(0, 1, 0.25), na.rm = FALSE,
  names = TRUE, type = 2, ...)

Arguments

x	numeric vector whose sample quantiles are wanted.
probs	numeric vector of probabilities with values in the range from 0 to 1.
na.rm	remove missing values NAs before computation?
names	include names of the probabilities, expressed as percentages?
type	an interger between 1 and 9 that selects the method for computing the quantile. See Note.
...	further arguments passed to or from other methods.

Value

An optionally named vector corresponding to the quantiles of x for the selected probabilities.

Note

Helsel and Hirsh (2002) define the 75th percentile as "a value which exceeds no more than 75 percent of the data and is exceeded by no more than 25 percent of the data." This rule can be easily extended to other percentiles. The selection of type equal to 2 ensures that this rule is met for all data. The rule stated by Helsel and Hirsch is very useful for an emprical description of the data, but Hyndman and Fan (1996) describe the slection of type for other applications.

References

Helsel, D.R. and Hirsch, R.M., 2002, Statistical methods in water resources: U.S. Geological Survey Techniques of Water-Resources Investigations, book 4, chap. A3, 522 p.

Hyndman, R.J. and Fan, Y. 1996, Sample quantiles in statistical packages: American Statistician, v. 50, p. 361-365.

See Also

quantile.default

Examples

# The default value for type (7) will compute a value that is exceeded by 4 values
#  for a sample of size 14
quantile(seq(14), type=7)
# But 4/14 is greater than 25 percent. But setting type to 2 will result in
#  only 3 values that are larger than the computed 75th percentile.
quantile(seq(14))

USGS-R/smwrStats documentation built on Oct. 11, 2022, 6:15 a.m.