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snanmskminabs

Calculate the minimum absolute value of a single-precision floating-point strided array according to a mask, ignoring NaN values.

Usage

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

snanmskminabs( N, x, strideX, mask, strideMask )

Computes the minimum absolute value of a single-precision floating-point strided arrays according to a mask, ignoring NaN values.

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );

var x = new Float32Array( [ 1.0, -2.0, -4.0, 2.0, NaN ] );
var mask = new Uint8Array( [ 0, 0, 1, 0, 0 ] );

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

The function has the following parameters:

  • N: number of indexed elements.
  • x: input Float32Array.
  • strideX: stride length for x.
  • mask: mask Uint8Array. If a mask array element is 0, the corresponding element in x is considered valid and included in computation. If a mask array element is 1, the corresponding element in x is considered invalid/missing and excluded from computation.
  • strideMask: stride length for mask.

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

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );

var x = new Float32Array( [ 1.0, 2.0, 7.0, -2.0, -4.0, 3.0, -5.0, -6.0 ] );
var mask = new Uint8Array( [ 0, 0, 0, 0, 0, 0, 1, 1 ] );

var v = snanmskminabs( 4, x, 2, mask, 2 );
// returns 1.0

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

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );

var x0 = new Float32Array( [ 2.0, 1.0, -2.0, -2.0, 3.0, 4.0, -5.0, -6.0 ] );
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var mask0 = new Uint8Array( [ 0, 0, 0, 0, 0, 0, 1, 1 ] );
var mask1 = new Uint8Array( mask0.buffer, mask0.BYTES_PER_ELEMENT*1 ); // start at 2nd element

var v = snanmskminabs( 4, x1, 2, mask1, 2 );
// returns 1.0

snanmskminabs.ndarray( N, x, strideX, offsetX, mask, strideMask, offsetMask )

Computes the minimum absolute value of a single-precision floating-point strided arrays according to a mask, ignoring NaN values and using alternative indexing semantics.

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );

var x = new Float32Array( [ 1.0, -2.0, -4.0, 2.0, NaN ] );
var mask = new Uint8Array( [ 0, 0, 1, 0, 0 ] );

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

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetMask: starting index for mask.

While typed array views mandate a view offset based on the underlying buffer, offset parameters support indexing semantics based on starting indices. For example, to calculate the minimum absolute value for every other element in x starting from the second element

var Float32Array = require( '@stdlib/array/float32' );
var Uint8Array = require( '@stdlib/array/uint8' );

var x = new Float32Array( [ 2.0, 1.0, -2.0, -2.0, 3.0, 4.0, -5.0, -6.0 ] );
var mask = new Uint8Array( [ 0, 0, 0, 0, 0, 0, 1, 1 ] );

var v = snanmskminabs.ndarray( 4, x, 2, 1, mask, 2, 1 );
// returns 1.0

Notes

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

Examples

var uniform = require( '@stdlib/random/base/uniform' );
var bernoulli = require( '@stdlib/random/base/bernoulli' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var snanmskminabs = require( '@stdlib/stats/strided/snanmskminabs' );

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 mask = filledarrayBy( x.length, 'uint8', bernoulli.factory( 0.2 ) );
console.log( mask );

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

C APIs

Usage

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

stdlib_strided_snanmskminabs( N, *X, strideX, *Mask, strideMask )

Computes the minimum absolute value of a single-precision floating-point strided array according to a mask, ignoring NaN values.

#include <stdint.h>

const float x[] = { 1.0f, -2.0f, 4.0f, 2.0f, 0.0f/0.0f };
const uint8_t mask[] = { 0, 0, 1, 0, 0 };

float v = stdlib_strided_snanmskminabs( 5, x, 1, mask, 1 );
// returns 1.0f

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.
  • Mask: [in] uint8_t* mask array. If a Mask array element is 0, the corresponding element in X is considered valid and included in computation. If a Mask array element is 1, the corresponding element in X is considered invalid/missing and excluded from computation.
  • strideMask: [in] CBLAS_INT stride length for Mask.
float stdlib_strided_snanmskminabs( const CBLAS_INT N, const float *X, const CBLAS_INT strideX, const uint8_t *Mask, const CBLAS_INT strideMask );

stdlib_strided_snanmskminabs_ndarray( N, *X, strideX, offsetX, *Mask, strideMask, offsetMask )

Computes the minimum absolute value of a single-precision floating-point strided array according to a mask, ignoring NaN values and using alternative indexing semantics.

#include <stdint.h>

const float x[] = { 1.0f, -2.0f, 4.0f, 2.0f, 0.0f/0.0f };
const uint8_t mask[] = { 0, 0, 1, 0, 0 };

float v = stdlib_strided_snanmskminabs_ndarray( 5, x, 1, 0, mask, 1, 0 );
// returns 1.0f

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.
  • Mask: [in] uint8_t* mask array. If a Mask array element is 0, the corresponding element in X is considered valid and included in computation. If a Mask array element is 1, the corresponding element in X is considered invalid/missing and excluded from computation.
  • strideMask: [in] CBLAS_INT stride length for Mask.
  • offsetMask: [in] CBLAS_INT starting index for Mask.
float stdlib_strided_snanmskminabs_ndarray( const CBLAS_INT N, const float *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, const uint8_t *Mask, const CBLAS_INT strideMask, const CBLAS_INT offsetMask );

Examples

#include "stdlib/stats/strided/snanmskminabs.h"
#include <stdint.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 };

    // Create a mask array:
    const uint8_t mask[] = { 0, 0, 0, 0, 0, 0, 0, 0, 1, 1 };

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

    // Specify the stride lengths:
    const int strideX = 2;
    const int strideMask = 2;

    // Compute the minimum absolute value:
    float v = stdlib_strided_snanmskminabs( N, x, strideX, mask, strideMask );

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