# weighted.mean: Weighted Arithmetic Mean

Description Usage Arguments Details Value See Also Examples

## Description

Compute a weighted mean.

## Usage

 ```1 2 3 4``` ```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 coerced to numeric by `as.numeric` and 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.

`mean`

## Examples

 ```1 2 3 4``` ```## 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) ```