Next Popular Module

# npm

## @stdlib/stats-base-dmediansorted 0.0.7 • Public • Published

# dmediansorted

Calculate the median value of a sorted double-precision floating-point strided array.

## Installation

npm install @stdlib/stats-base-dmediansorted

## Usage

var dmediansorted = require( '@stdlib/stats-base-dmediansorted' );

#### dmediansorted( N, x, stride )

Computes the median value of a sorted double-precision floating-point strided array x.

var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0 ] );
var v = dmediansorted( x.length, x, 1 );
// returns 2.0

x = new Float64Array( [ 3.0, 2.0, 1.0 ] );
v = dmediansorted( x.length, x, 1 );
// returns 2.0

The function has the following parameters:

The N and stride parameters determine which elements in x are accessed at runtime. For example, to compute the median value of every other element in x,

var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, 3.0, 3.0, 4.0, 2.0 ] );
var N = floor( x.length / 2 );

var v = dmediansorted( N, x, 2 );
// returns 2.5

Note that indexing is relative to the first index. To introduce an offset, use typed array views.

var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );

var x0 = new Float64Array( [ 2.0, 1.0, 2.0, 2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var N = floor( x0.length / 2 );

var v = dmediansorted( N, x1, 2 );
// returns 2.0

#### dmediansorted.ndarray( N, x, stride, offset )

Computes the median value of a sorted double-precision floating-point strided array using alternative indexing semantics.

var Float64Array = require( '@stdlib/array-float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0 ] );
var N = x.length;

var v = dmediansorted.ndarray( N, x, 1, 0 );
// returns 2.0

The function has the following additional parameters:

• offset: starting index for x.

While typed array views mandate a view offset based on the underlying buffer, the offset parameter supports indexing semantics based on a starting index. For example, to calculate the median value for every other value in x starting from the second value

var Float64Array = require( '@stdlib/array-float64' );
var floor = require( '@stdlib/math-base-special-floor' );

var x = new Float64Array( [ 2.0, 1.0, 2.0, 2.0, -2.0, 2.0, 3.0, 4.0 ] );
var N = floor( x.length / 2 );

var v = dmediansorted.ndarray( N, x, 2, 1 );
// returns 2.0

## Notes

• If N <= 0, both functions return NaN.
• The input strided array must be sorted in either strictly ascending or descending order.

## Examples

var Float64Array = require( '@stdlib/array-float64' );
var dmediansorted = require( '@stdlib/stats-base-dmediansorted' );

var x;
var i;

x = new Float64Array( 10 );
for ( i = 0; i < x.length; i++ ) {
x[ i ] = i - 5.0;
}
console.log( x );

var v = dmediansorted( x.length, x, 1 );
console.log( v );

## Notice

This package is part of stdlib, a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop stdlib, see the main project repository.

#### Community ### Install

npm i @stdlib/stats-base-dmediansorted

### Repository

github.com/stdlib-js/stats-base-dmediansorted

stdlib.io

17

0.0.7