README.md

drangeabs

Calculate the range of absolute values of a double-precision floating-point strided array.

The range is defined as the difference between the maximum and minimum values.

Usage

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

drangeabs( N, x, strideX )

Computes the range of absolute values of a double-precision floating-point strided array.

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

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

var v = drangeabs( x.length, x, 1 );
// returns 1.0

The function has the following parameters:

• N: number of indexed elements.
• x: input Float64Array.
• strideX: stride length for x.

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

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

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

var v = drangeabs( 4, x, 2 );
// returns 3.0

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 = drangeabs( 4, x1, 2 );
// returns 3.0

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

Computes the range of absolute values of a double-precision floating-point strided array using alternative indexing semantics.

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

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

var v = drangeabs.ndarray( x.length, x, 1, 0 );
// returns 1.0

The function has the following additional parameters:

• offsetX: 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 range of absolute values for every other element in x starting from the second element

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 = drangeabs.ndarray( 4, x, 2, 1 );
// returns 3.0

Notes

• If N <= 0, both functions return NaN.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var drangeabs = require( '@stdlib/stats/strided/drangeabs' );

var x = discreteUniform( 10, -50, 50, {
    'dtype': 'float64'
});
console.log( x );

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

---

C APIs

Usage

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

stdlib_strided_drangeabs( N, *X, strideX )

Computes the range of absolute values of a double-precision floating-point strided array.

const double x[] = { 1.0, -2.0, 3.0, -4.0 };

double v = stdlib_strided_drangeabs( 4, x, 1 );
// returns 3.0

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

stdlib_strided_drangeabs_ndarray( N, *X, strideX, offsetX )

Computes the range of absolute values of a double-precision floating-point strided array using alternative indexing semantics.

const double x[] = { 1.0, -2.0, 3.0, -4.0 };

double v = stdlib_strided_drangeabs_ndarray( 4, x, 1, 0 );
// returns 3.0

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

Examples

#include "stdlib/stats/strided/drangeabs.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 range:
    double v = stdlib_strided_drangeabs( N, x, strideX );

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