7.6 KiB
dabs
Compute the absolute value for each element in a double-precision floating-point strided array.
Usage
var dabs = require( '@stdlib/math/strided/special/dabs' );
dabs( N, x, strideX, y, strideY )
Computes the absolute value for each element in a double-precision floating-point strided array x
and assigns the results to elements in a double-precision floating-point strided array y
.
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ] );
// Compute the absolute values in-place:
dabs( x.length, x, 1, x, 1 );
// x => <Float64Array>[ 2.0, 1.0, 3.0, 5.0, 4.0, 0.0, 1.0, 3.0 ]
The function accepts the following arguments:
- N: number of indexed elements.
- x: input
Float64Array
. - strideX: index increment for
x
. - y: output
Float64Array
. - strideY: index increment for
y
.
The N
and stride
parameters determine which elements in x
and y
are accessed at runtime. For example, to index every other value in x
and to index the first N
elements of y
in reverse order,
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var N = floor( x.length / 2 );
dabs( N, x, 2, y, -1 );
// y => <Float64Array>[ 5.0, 3.0, 1.0, 0.0, 0.0, 0.0 ]
Note that indexing is relative to the first index. To introduce an offset, use typed array
views.
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );
// Initial arrays...
var x0 = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y0 = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
// Create offset views...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Float64Array( y0.buffer, y0.BYTES_PER_ELEMENT*3 ); // start at 4th element
var N = floor( x0.length / 2 );
dabs( N, x1, -2, y1, 1 );
// y0 => <Float64Array>[ 0.0, 0.0, 0.0, 6.0, 4.0, 2.0 ]
dabs.ndarray( N, x, strideX, offsetX, y, strideY, offsetY )
Computes the absolute value for each element in a double-precision floating-point strided array x
and assigns the results to elements in a double-precision floating-point strided array y
using alternative indexing semantics.
var Float64Array = require( '@stdlib/array/float64' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0 ] );
dabs.ndarray( x.length, x, 1, 0, y, 1, 0 );
// y => <Float64Array>[ 1.0, 2.0, 3.0, 4.0, 5.0 ]
The function accepts the following additional arguments:
- offsetX: starting index for
x
. - offsetY: starting index for
y
.
While typed array
views mandate a view offset based on the underlying buffer
, the offsetX
and offsetY
parameters support indexing semantics based on starting indices. For example, to index every other value in x
starting from the second value and to index the last N
elements in y
,
var Float64Array = require( '@stdlib/array/float64' );
var floor = require( '@stdlib/math/base/special/floor' );
var x = new Float64Array( [ -1.0, -2.0, -3.0, -4.0, -5.0, -6.0 ] );
var y = new Float64Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
var N = floor( x.length / 2 );
dabs.ndarray( N, x, 2, 1, y, -1, y.length-1 );
// y => <Float64Array>[ 0.0, 0.0, 0.0, 6.0, 4.0, 2.0 ]
Examples
var round = require( '@stdlib/math/base/special/round' );
var randu = require( '@stdlib/random/base/randu' );
var Float64Array = require( '@stdlib/array/float64' );
var dabs = require( '@stdlib/math/strided/special/dabs' );
var x = new Float64Array( 10 );
var y = new Float64Array( 10 );
var i;
for ( i = 0; i < x.length; i++ ) {
x[ i ] = round( (randu()*200.0) - 100.0 );
}
console.log( x );
console.log( y );
dabs.ndarray( x.length, x, 1, 0, y, -1, y.length-1 );
console.log( y );
C APIs
Usage
#include "stdlib/math/strided/special/dabs.h"
stdlib_strided_dabs( N, *X, strideX, *Y, strideY )
Computes the absolute value for each element in a double-precision floating-point strided array X
and assigns the results to elements in a double-precision floating-point strided array Y
.
#include <stdint.h>
double X[] = { -1.0, -2.0, -3.0, -4.0, -5.0, -6.0, -7.0, -8.0 };
double Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
int64_t N = 4;
stdlib_strided_dabs( N, X, 2, Y, 2 );
The function accepts the following arguments:
- N:
[in] int64_t
number of indexed elements. - X:
[in] double*
input array. - strideX:
[in] int64_t
index increment forX
. - Y:
[out] double*
output array. - strideY:
[in] int64_t
index increment forY
.
void stdlib_strided_dabs( const int64_t N, const double *X, const int64_t strideX, double *Y, const int64_t strideY );
Examples
#include "stdlib/math/strided/special/dabs.h"
#include <stdint.h>
#include <stdio.h>
int main() {
// Create an input strided array:
double X[] = { -1.0, -2.0, -3.0, -4.0, -5.0, -6.0, -7.0, -8.0 };
// Create an output strided array:
double Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
// Specify the number of elements:
int64_t N = 4;
// Specify the stride lengths:
int64_t strideX = 2;
int64_t strideY = 2;
// Compute the absolute value element-wise:
stdlib_strided_dabs( N, X, strideX, Y, strideY );
// Print the result:
for ( int i = 0; i < 8; i++ ) {
printf( "Y[ %i ] = %lf\n", i, Y[ i ] );
}
}