README.md

snancount

Calculate the number of non-NaN elements in a single-precision floating-point strided array.

Usage

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

snancount( N, x, strideX )

Computes the number of non-NaN elements in a single-precision floating-point strided array.

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

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

var v = snancount( x.length, x, 1 );
// returns 3

The function has the following parameters:

• N: number of indexed elements.
• x: input Float32Array.
• strideX: stride length for x.

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

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

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

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

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

var v = snancount( 4, x1, 2 );
// returns 3

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

Computes the number of non-NaN elements in a single-precision floating-point strided array using alternative indexing semantics.

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

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

var v = snancount.ndarray( 4, x, 2, 1 );
// returns 3

The function has the following additional parameter:

• 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 count every other element in x starting from the second element,

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

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

var v = snancount.ndarray( 4, x, 2, 1 );
// returns 3

Notes

• If N <= 0, both functions return 0.

Examples

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

function rand() {
    if ( bernoulli( 0.8 ) < 1 ) {
        return NaN;
    }
    return uniform( -50.0, 50.0 );
}

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

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

---

C APIs

Usage

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

stdlib_strided_snancount( N, *X, strideX )

Computes the number of non-NaN elements in a single-precision floating-point strided array.

const float x[] = { 1.0f, 2.0f, 0.0f / 0.0f, 4.0f, 5.0f, 6.0f, 0.0f / 0.0f, 8.0f };

int v = stdlib_strided_snancount( 4, x, 2 );
// returns 2

The function accepts the following arguments:

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

CBLAS_INT stdlib_strided_snancount( const CBLAS_INT N, const float *X, const CBLAS_INT strideX );

stdlib_strided_snancount_ndarray( N, *X, strideX, offsetX )

Computes the number of non-NaN elements in a single-precision floating-point strided array using alternative indexing semantics.

const float x[] = { 2.0f, 1.0f, 0.0f / 0.0f, -2.0f, 3.0f, 4.0f, 0.0f / 0.0f, 0.0f / 0.0f };

int v = stdlib_strided_snancount_ndarray( 4, x, 2, 1 );
// returns 3

The function accepts the following arguments:

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

CBLAS_INT stdlib_strided_snancount_ndarray( const CBLAS_INT N, const float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX );

Notes

• If N <= 0, both functions return 0.

Examples

#include "stdlib/blas/ext/base/snancount.h"
#include <stdio.h>

int main( void ) {
    // Create a strided array:
    const float x[] = { 1.0f, 2.0f, 3.0f, 4.0f, 5.0f, 6.0f, 7.0f, 8.0f, 0.0f/0.0f, 0.0f/0.0f };

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

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

    // Compute the number of non-NaN elements:
    int v = stdlib_strided_snancount( N, x, strideX );

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