scumaxabs

Calculate the cumulative maximum absolute value of single-precision floating-point strided array elements.

Usage

var scumaxabs = require( '@stdlib/stats/base/scumaxabs' );

scumaxabs( N, x, strideX, y, strideY )

Computes the cumulative maximum absolute value of single-precision floating-point strided array elements.

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

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

scumaxabs( x.length, x, 1, y, 1 );
// y => <Float32Array>[ 1.0, 2.0, 2.0 ]

The function has the following parameters:

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

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

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

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

var v = scumaxabs( 4, x, 2, y, 1 );
// y => <Float32Array>[ 1.0, 2.0, 2.0, 4.0, 0.0, 0.0, 0.0, 0.0 ]

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

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

// Initial arrays...
var x0 = new Float32Array( [ 2.0, 1.0, 2.0, -2.0, -2.0, 2.0, 3.0, 4.0 ] );
var y0 = new Float32Array( x0.length );

// Create offset views...
var x1 = new Float32Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float32Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element

scumaxabs( 4, x1, -2, y1, 1 );
// y0 => <Float32Array>[ 0.0, 0.0, 0.0, 4.0, 4.0, 4.0, 4.0, 0.0 ]

scumaxabs.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )

Computes the cumulative maximum absolute value of single-precision floating-point strided array elements using alternative indexing semantics.

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

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

scumaxabs.ndarray( x.length, x, 1, 0, y, 1, 0 );
// y => <Float32Array>[ 1.0, 2.0, 2.0 ]

The function has the following additional parameters:

  • offsetX: starting index for x.
  • offsetY: starting index for y.

While typed array views mandate a view offset based on the underlying buffer, offset parameters support indexing semantics based on a starting indices. For example, to calculate the cumulative maximum absolute value of every other element in x starting from the second element and to store in the last N elements of y starting from the last element

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

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

scumaxabs.ndarray( 4, x, 2, 1, y, -1, y.length-1 );
// y => <Float32Array>[ 0.0, 0.0, 0.0, 0.0, 4.0, 2.0, 2.0, 1.0 ]

Notes

  • If N <= 0, both functions return y unchanged.

Examples

var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var Float32Array = require( '@stdlib/array/float32' );
var scumaxabs = require( '@stdlib/stats/base/scumaxabs' );

var x = discreteUniform( 10, -50, 50, {
    'dtype': 'float32'
});
var y = new Float32Array( x.length );
console.log( x );
console.log( y );

scumaxabs( x.length, x, 1, y, -1 );
console.log( y );

C APIs

Usage

#include "stdlib/stats/base/scumaxabs.h"

stdlib_strided_scumaxabs( N, *X, strideX, *Y, strideY )

Computes the cumulative maximum absolute value of single-precision floating-point strided array elements.

const float x[] = { 1.0f, 2.0f, -3.0f, 4.0f, -5.0f, 6.0f, 7.0f, 8.0f };
float y[] = { 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f, 0.0f };

stdlib_strided_scumaxabs( 4, x, 2, y, -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.
  • Y: [out] float* output array.
  • strideY: [in] CBLAS_INT stride length for Y.
void stdlib_strided_scumaxabs( const CBLAS_INT N, const float *X, const CBLAS_INT strideX, float *Y, const CBLAS_INT strideY );

stdlib_strided_scumaxabs_ndarray(N, *X, strideX, offsetX, *Y, strideY, offsetY )

Computes the cumulative maximum absolute value of single-precision floating-point strided array elements using alternative indexing semantics.

#include "stdlib/stats/base/scumaxabs.h"
#include <stdio.h>

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

    // Specify the number of elements:
    const int N = 4;

    // Specify stride lengths:
    const int strideX = 2;
    const int strideY = -2;

    // Compute the cumulative maximum absolute value:
    stdlib_strided_scumaxabs( N, x, strideX, y, strideY );

    // Print the result:
    for ( int i = 0; i < 8; i++ ) {
        printf( "y[ %d ] = %f\n", i, y[ i ] );
    }
}

See Also

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