@stdlib/blas-ext-base-sdsnansum

v0.2.2

Published

4 months ago

Calculate the sum of single-precision floating-point strided array elements, ignoring NaN values and using extended accumulation.

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sdsnansum

Calculate the sum of single-precision floating-point strided array elements, ignoring NaN values and using extended accumulation.

Installation

npm install @stdlib/blas-ext-base-sdsnansum

Usage

var sdsnansum = require( '@stdlib/blas-ext-base-sdsnansum' );

sdsnansum( N, x, stride )

Computes the sum of single-precision floating-point strided array elements, ignoring NaN values and using extended accumulation.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );

var v = sdsnansum( 4, x, 1 );
// returns 1.0

The function has the following parameters:

N: number of indexed elements.
x: input Float32Array.
stride: index increment for the strided array.

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

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, 2.0, NaN, -7.0, NaN, 3.0, 4.0, 2.0 ] );

var v = sdsnansum( 4, x, 2 );
// returns 5.0

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

var Float32Array = require( '@stdlib/array-float32' );

var x0 = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var v = sdsnansum( 4, x1, 2 );
// returns 5.0

sdsnansum.ndarray( N, x, stride, offset )

Computes the sum of single-precision floating-point strided array elements, ignoring NaN values and using extended accumulation and alternative indexing semantics.

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 1.0, -2.0, NaN, 2.0 ] );
var N = x.length;

var v = sdsnansum.ndarray( N, x, 1, 0 );
// returns 1.0

The function has the following additional parameters:

offset: starting index for the strided array.

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 sum of every other value in the strided array starting from the second value

var Float32Array = require( '@stdlib/array-float32' );

var x = new Float32Array( [ 2.0, 1.0, NaN, -2.0, -2.0, 2.0, 3.0, 4.0 ] );

var v = sdsnansum.ndarray( 4, x, 2, 1 );
// returns 5.0

Notes

If N <= 0, both functions return 0.0.
Accumulated intermediate values are stored as double-precision floating-point numbers.

Examples

var discreteUniform = require( '@stdlib/random-base-discrete-uniform' );
var bernoulli = require( '@stdlib/random-base-bernoulli' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var sdsnansum = require( '@stdlib/blas-ext-base-sdsnansum' );

function randOrNan() {
    if ( bernoulli() < 0.2 ) {
        return NaN;
    }
    return discreteUniform( 0, 100 );
}

var x = filledarrayBy( 10, 'float32', randOrNan );
console.log( x );

var v = sdsnansum( 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.

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See LICENSE.

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