dnanasum

Calculate the sum of absolute values (L1 norm) of double-precision floating-point strided array elements, ignoring NaN values.

The L1 norm is defined as

Usage

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

dnanasum( N, x, strideX )

Computes the sum of absolute values (L1 norm) of double-precision floating-point strided array elements, ignoring NaN values.

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

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

var v = dnanasum( N, x, 1 );
// returns 5.0

The function has the following parameters:

  • N: number of indexed elements.
  • x: 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 sum of absolute values (L1 norm) for every other element in the strided array,

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

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

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

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, NaN, -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 = dnanasum( 4, x1, 2 );
// returns 9.0

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

Computes the sum of absolute values (L1 norm) of double-precision floating-point strided array elements, ignoring NaN values and using alternative indexing semantics.

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

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

var v = dnanasum.ndarray( 4, x, 1, 0 );
// returns 5.0

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 sum of absolute values (L1 norm) for every other value in the strided array starting from the second value

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

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

var v = dnanasum.ndarray( 4, x, 2, 1 );
// returns 9.0

Notes

  • If N <= 0, both functions return 0.0.

Examples

var bernoulli = require( '@stdlib/random/base/bernoulli' );
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var Float64Array = require( '@stdlib/array/float64' );
var dnanasum = require( '@stdlib/blas/ext/base/dnanasum' );

function rand() {
    if ( bernoulli( 0.8 ) > 0 ) {
        return discreteUniform( 0, 100 );
    }
    return NaN;
}

var x = filledarrayBy( 10, 'float64', rand );
console.log( x );

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

C APIs

Usage

#include "stdlib/blas/ext/base/dnanasum.h"

stdlib_strided_dnanasum( N, *X, strideX )

Computes the sum of absolute values (L1 norm) of double-precision floating-point strided array elements, ignoring NaN values.

const double x[] = { 1.0, 2.0, 0.0/0.0, 4.0 };

double v = stdlib_strided_dnanasum( 4, x, 1 );
// returns 7.0

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • X: [in] double* input array.
  • strideX: [in] CBLAS_INT index increment for X.
double stdlib_strided_dnanasum( const CBLAS_INT N, const double *X, const CBLAS_INT strideX );

stdlib_strided_dnanasum_ndarray( N, *X, strideX, offsetX )

Computes the sum of absolute values (L1 norm) of double-precision floating-point strided array elements, ignoring NaN values and using alternative indexing semantics.

const double x[] = { 1.0, 2.0, 0.0/0.0, 4.0 };

double v = stdlib_strided_dnanasum_ndarray( 4, x, 1, 0 );
// returns 7.0

The function accepts the following arguments:

  • N: [in] CBLAS_INT number of indexed elements.
  • X: [in] double* input array.
  • strideX: [in] CBLAS_INT index increment for X.
  • offsetX: [in] CBLAS_INT starting index for X.
double stdlib_strided_dnanasum_ndarray( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Examples

#include "stdlib/blas/ext/base/dnanasum.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, 0.0/0.0, 0.0/0.0 };

    // Specify the number of elements:
    const int N = 5;

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

    // Compute the sum:
    double v = stdlib_strided_dnanasum( N, x, strideX );

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

See Also

Did you find this page helpful?