dmediansorted

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

Installation

npm install @stdlib/stats-strided-dmediansorted

Usage

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

dmediansorted( N, x, strideX )

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:

• N: number of indexed elements.
• x: sorted input Float64Array.
• strideX: index increment for x.

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

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

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, 3.0, 3.0, 4.0, 2.0 ] );

var v = dmediansorted( 4, 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 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 v = dmediansorted( 4, x1, 2 );
// returns 2.0

dmediansorted.ndarray( N, x, strideX, offsetX )

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 v = dmediansorted.ndarray( x.length, 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 x = new Float64Array( [ 2.0, 1.0, 2.0, 2.0, -2.0, 2.0, 3.0, 4.0 ] );

var v = dmediansorted.ndarray( 4, 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 linspace = require( '@stdlib/array-linspace' );
var dmediansorted = require( '@stdlib/stats-strided-dmediansorted' );

var options = {
    'dtype': 'float64'
};
var x = linspace( -5.0, 5.0, 10, options );
console.log( x );

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

C APIs

Usage

#include "stdlib/stats/strided/dmediansorted.h"

stdlib_strided_dmediansorted( N, *X, strideX )

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

const double x[] = { 1.0, 2.0, 3.0 };

double v = stdlib_strided_dmediansorted( 3, x, 1 );
// returns 2.0

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• X: [in] double* input array.
• strideX: [in] CBLAS_INT stride length for X.

double stdlib_strided_dmediansorted( const CBLAS_INT N, const double *X, const CBLAS_INT strideX );

stdlib_strided_dmediansorted_ndarray( N, *X, strideX, offsetX )

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

const double x[] = { 1.0, 2.0, 3.0 };

double v = stdlib_strided_dmediansorted_ndarray( 3, x, 1, 0 );
// returns 2.0

The function accepts the following arguments:

• N: [in] CBLAS_INT number of indexed elements.
• X: [in] double* input array.
• strideX: [in] CBLAS_INT stride length for X.
• offsetX: [in] CBLAS_INT starting index for X.

double stdlib_strided_dmediansorted_ndarray( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/stats/strided/dmediansorted.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array:
    const double x[] = { 1.0, 2.0, 3.0, 4.0, 5.0, 6.0, 7.0, 8.0 };

    // Specify the number of elements:
    const int N = 4;

    // Specify the stride length:
    const int strideX = 2;

    // Compute the median value:
    double v = stdlib_strided_dmediansorted( N, x, strideX );

    // Print the result:
    printf( "median: %lf\n", v );
}

See Also

• @stdlib/stats-strided/dmean: calculate the arithmetic mean of a double-precision floating-point strided array.
• @stdlib/stats-strided/mediansorted: calculate the median value of a sorted strided array.
• @stdlib/stats-strided/smediansorted: calculate the median value of a sorted single-precision floating-point strided array.

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

License

See LICENSE.

Copyright

Copyright © 2016-2026. The Stdlib Authors.