Product
Computes the product.
The product 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-prod
For use in the browser, use browserify.
Usage
var prod = ;
prod( x[, options] )
Computes the product of the elements in x
. x
may be either an array
, typed array
, or matrix
.
var data = 1 2 3 4 ;var p = ;// returns 24data = data ;p = ;// returns 24
For non-numeric arrays
, provide an accessor function
for accessing array
values.
var arr ='x':1'x':2'x':3'x':4;{return dx;}var value =;// returns 24
If provided a matrix
, the function accepts the following options
:
- dim: dimension along which to compute the product. Default:
2
(along the columns). - dtype: output
matrix
data type. Default:float64
.
By default, the function computes the product along the columns (dim=2
).
var matrix =datamatpi;data = 9 ;for i = 0; i < datalength; i++data i = i + 1;mat = ;/*[ 1 2 34 5 67 8 9 ]*/p = ;/*[ 6120504 ]*/
To compute the product along the rows, set the dim
option to 1
.
p =;/*[ 28 80 162 ]*/
By default, the output matrix
data type is float64
. To specify a different output data type, set the dtype
option.
p =;/*[ 28 80 162 ]*/var dtype = pdtype;// 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 ;// Row vector:mat = ;p = ;// returns 40// Column vector:mat = ;p = ;// returns 40
If provided an empty array
, typed array
, or matrix
, the function returns the empty product which is equal to 1
.
p = ;// returns 1p = ;// returns 1p = ;// returns 1p = ;// returns 1p = ;// returns 1
Examples
var matrix =prod = ;var datamatpi;// Plain arrays...var data = 100 ;for var i = 0; i < datalength; i++data i = Math;p = ;// Object arrays (accessors)...{return dx;}for i = 0; i < datalength; i++data i ='x': data i;p =;// Typed arrays...data = 100 ;for i = 0; i < datalength; i++data i = Math;p = ;// Matrices (along rows)...mat = ;p =;// Matrices (along columns)...p =;// Matrices (custom output data type)...p =;
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 © 2015. The Compute.io Authors.