Mean
Computes the arithmetic mean.
The arithmetic mean is defined as
where x_0, x_1,...,x_{N-1}
are individual data values and N
is the total number of values in the data set.
Installation
$ npm install compute-mean
Usage
var mean = ;
mean( x[, opts] )
Computes the arithmetic mean. x
may be either an array
, typed array
, or matrix
.
var data mu;data = 2 4 5 3 8 2 ;mu = ;// returns 4data = data ;mu = ;// returns 4
For non-numeric arrays
, provide an accessor function
for accessing array
values.
var data ='x':2'x':4'x':5'x':3'x':8'x':2;{return dx;}var mu =;// returns 4
If provided a matrix
, the function accepts the following options
:
- dim: dimension along which to compute the arithmetic mean. Default:
2
(along the columns). - dtype: output
matrix
data type. Default:float64
.
By default, the function computes the arithmetic mean along the columns (dim=2
).
var matrix =datamatmui;data = 25 ;for i = 0; i < datalength; i++data i = i;mat = ;/*[ 0 1 2 3 45 6 7 8 910 11 12 13 1415 16 17 18 1920 21 22 23 24 ]*/mu = ;/*[ 27121722 ]*/
To compute the arithmetic mean along the rows, set the dim
option to 1
.
mu =;/*[ 10, 11, 12, 13, 14 ]*/
By default, the output matrix
data type is float64
. To specify a different output data type, set the dtype
option.
mu =;/*[ 10, 11, 12, 13, 14 ]*/var dtype = mudtype;// returns 'uint8'
If provided a matrix
having either dimension equal to 1
, the function treats the matrix
as a typed array
and returns a numeric
value.
data = 2 4 5 3 8 2 ;// Row vector:mat = ;mu = ;// returns 4// Column vector:mat = ;mu = ;// returns 4
If provided an empty array
, typed array
, or matrix
, the function returns null
.
mu = ;// returns nullmu = ;// returns nullmu = ;// returns nullmu = ;// returns nullmu = ;// returns null
Examples
var matrix =mean = ;var datamatmui;// Plain arrays...data = 1000 ;for i = 0; i < datalength; i++data i = Math * 100;mu = ;// Object arrays (accessors)...{return dx;}for i = 0; i < datalength; i++data i = 'x': data i ;mu =;// Typed arrays...data = 1000 ;for i = 0; i < datalength; i++data i = Math * 100;mu = ;// Matrices (along rows)...mat = ;mu =;// Matrices (along columns)...mu =;// Matrices (custom output data type)...mu =;
To run the example code from the top-level application directory,
$ node ./examples/index.js
Tests
Unit
Unit tests use the Mocha test framework with Chai assertions. To run the tests, execute the following command in the top-level application directory:
$ make test
All new feature development should have corresponding unit tests to validate correct functionality.
Test Coverage
This repository uses Istanbul as its code coverage tool. To generate a test coverage report, execute the following command in the top-level application directory:
$ make test-cov
Istanbul creates a ./reports/coverage
directory. To access an HTML version of the report,
$ make view-cov
License
Copyright
Copyright © 2014-2015. The Compute.io Authors.