stdlib-js
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About stdlib...
</summary>
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dapx
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Add a constant to each element in a double-precision floating-point strided array.
bash
npm install @stdlib/blas-ext-base-dapx
javascript
var dapx = require( '@stdlib/blas-ext-base-dapx' );
#### dapx( N, alpha, x, stride )
Adds a constant alpha to each element in a double-precision floating-point strided array.
javascript
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 ] );
dapx( x.length, 5.0, x, 1 );
// x => <Float64Array>[ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
The function has the following parameters:
- N: number of indexed elements.
- alpha: scalar constant.
- x: input [Float64Array][@stdlib/array/float64].
- stride: index increment.
The N and stride parameters determine which elements in the strided array are accessed at runtime. For example, to add a constant to every other element
javascript
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 ] );
dapx( 4, 5.0, x, 2 );
// x => <Float64Array>[ 3.0, 1.0, 8.0, -5.0, 9.0, 0.0, 4.0, -3.0 ]
Note that indexing is relative to the first index. To introduce an offset, use [typed array][mdn-typed-array] views.
javascript
var Float64Array = require( '@stdlib/array-float64' );
// Initial array...
var x0 = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
// Create an offset view...
var x1 = new Float64Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
// Add a constant to every other element...
dapx( 3, 5.0, x1, 2 );
// x0 => <Float64Array>[ 1.0, 3.0, 3.0, 1.0, 5.0, -1.0 ]
#### dapx.ndarray( N, alpha, x, stride, offset )
Adds a constant alpha to each element in a double-precision floating-point strided array using alternative indexing semantics.
javascript
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 ] );
dapx.ndarray( x.length, 5.0, x, 1, 0 );
// x => <Float64Array>[ 3.0, 6.0, 8.0, 0.0, 9.0, 5.0, 4.0, 2.0 ]
The function has the following additional parameters:
- offset: starting index.
While [typed array][mdn-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 access only the last three elements of the strided array
javascript
var Float64Array = require( '@stdlib/array-float64' );
var x = new Float64Array( [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ] );
dapx.ndarray( 3, 5.0, x, 1, x.length-3 );
// x => <Float64Array>[ 1.0, -2.0, 3.0, 1.0, 10.0, -1.0 ]
N <= 0, both functions return the strided array unchanged.
javascript
var discreteUniform = require( '@stdlib/random-base-discrete-uniform' ).factory;
var filledarrayBy = require( '@stdlib/array-filled-by' );
var dapx = require( '@stdlib/blas-ext-base-dapx' );
var x = filledarrayBy( 10, 'float64', discreteUniform( -100, 100 ) );
console.log( x );
dapx( x.length, 5.0, x, 1 );
console.log( x );
@stdlib/blas-ext/base/gapx][@stdlib/blas/ext/base/gapx]: add a constant to each element in a strided array.
- [@stdlib/blas-ext/base/sapx][@stdlib/blas/ext/base/sapx]: add a constant to each element in a single-precision floating-point strided array.
