weighted.mean {stats}

R Documentation

Weighted Arithmetic Mean

Description

Compute a weighted mean.

Usage

weighted.mean(x, w, ...)

## Default S3 method:
weighted.mean(x, w, ..., na.rm = FALSE)

Arguments

x	an object containing the values whose weighted mean is to be computed.
w	a numerical vector of weights the same length as x giving the weights to use for elements of x.
...	arguments to be passed to or from methods.
na.rm	a logical value indicating whether NA values in x should be stripped before the computation proceeds.

Details

This is a generic function and methods can be defined for the first argument x: apart from the default methods there are methods for the date-time classes "POSIXct", "POSIXlt", "difftime" and "Date". The default method will work for any numeric-like object for which [, multiplication, division and sum have suitable methods, including complex vectors.

If w is missing then all elements of x are given the same weight, otherwise the weights are normalized to sum to one (if possible: if their sum is zero or infinite the value is likely to be NaN).

Missing values in w are not handled specially and so give a missing value as the result. However, zero weights are handled specially and the corresponding x values are omitted from the sum.

Value

For the default method, a length-one numeric vector.

See Also

mean

Examples

## GPA from Siegel 1994
wt <- c(5,  5,  4,  1)/15
x <- c(3.7,3.3,3.5,2.8)
xm <- weighted.mean(x, wt)

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