@stdlib/strided
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Strided.
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# zmap
> Apply a unary function to a double-precision floating-point strided input array and assign results to a double-precision floating-point strided output array.
<section class="intro">
</section>
<!-- /.intro -->
<section class="usage">
## Usage
```javascript
var zmap = require( '@stdlib/strided/base/zmap' );
```
#### zmap( N, x, strideX, y, strideY, fcn )
Applies a unary function to a double-precision complex floating-point strided input array and assigns results to a double-precision complex floating-point strided output array.
```javascript
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var cceil = require( '@stdlib/math/base/special/cceil' );
var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );
zmap( x.length, x, 1, y, 1, cceil );
var v = y.get( 0 );
// returns <Complex128>
var re = real( v );
// returns -2.0
var im = imag( v );
// returns 2.0
```
The function accepts the following arguments:
- **N**: number of indexed elements.
- **x**: input [`Complex128Array`][@stdlib/array/complex128].
- **strideX**: index increment for `x`.
- **y**: output [`Complex128Array`][@stdlib/array/complex128].
- **strideY**: index increment for `y`.
- **fcn**: function to apply.
The `N` and stride parameters determine which elements in the strided arrays 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,
```javascript
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var cceil = require( '@stdlib/math/base/special/cceil' );
var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );
zmap( 2, x, 2, y, -1, cceil );
var v = y.get( 0 );
// returns <Complex128>
var re = real( v );
// returns 5.0
var im = imag( v );
// returns 0.0
```
Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][@stdlib/array/complex128] views.
```javascript
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var cceil = require( '@stdlib/math/base/special/cceil' );
// Initial arrays...
var x0 = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y0 = new Complex128Array( [ 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 ] );
// Create offset views...
var x1 = new Complex128Array( x0.buffer, x0.BYTES_PER_ELEMENT*1 ); // start at 2nd element
var y1 = new Complex128Array( y0.buffer, y0.BYTES_PER_ELEMENT*2 ); // start at 3rd element
zmap( 2, x1, -2, y1, 1, cceil );
var v = y0.get( 2 );
// returns <Complex128>
var re = real( v );
// returns -1.0
var im = imag( v );
// returns 4.0
```
#### zmap.ndarray( N, x, strideX, offsetX, y, strideY, offsetY, fcn )
Applies a unary function to a double-precision complex floating-point strided input array and assigns results to a double-precision complex floating-point strided output array using alternative indexing semantics.
```javascript
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var cceil = require( '@stdlib/math/base/special/cceil' );
var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );
zmap.ndarray( x.length, x, 1, 0, y, 1, 0, cceil );
var v = y.get( 0 );
// returns <Complex128>
var re = real( v );
// returns -2.0
var im = imag( v );
// returns 2.0
```
The function accepts the following additional arguments:
- **offsetX**: starting index for `x`.
- **offsetY**: starting index for `y`.
While [`typed array`][@stdlib/array/complex128] views mandate a view offset based on the underlying `buffer`, the offset 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` in reverse order,
```javascript
var Complex128Array = require( '@stdlib/array/complex128' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var cceil = require( '@stdlib/math/base/special/cceil' );
var x = new Complex128Array( [ -2.3, 1.5, 3.1, -5.2, 4.8, 0.0, -1.6, 3.4 ] );
var y = new Complex128Array( x.length );
zmap.ndarray( 2, x, 2, 1, y, -1, y.length-1, cceil );
var v = y.get( y.length-1 );
// returns <Complex128>
var re = real( v );
// returns 4.0
var im = imag( v );
// returns -5.0
```
</section>
<!-- /.usage -->
<section class="notes">
</section>
<!-- /.notes -->
<section class="examples">
## Examples
<!-- eslint no-undef: "error" -->
```javascript
var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
var Complex128Array = require( '@stdlib/array/complex128' );
var filledarrayBy = require( '@stdlib/array/filled-by' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );
var Complex128 = require( '@stdlib/complex/float64/ctor' );
var zmap = require( '@stdlib/strided/base/zmap' );
function scale( x ) {
var re = real( x );
var im = imag( x );
return new Complex128( re*10.0, im*10.0 );
}
var xbuf = filledarrayBy( 10*2, 'float64', discreteUniform( -100.0, 100.0 ) );
var x = new Complex128Array( xbuf.buffer );
console.log( x );
var y = new Complex128Array( x.length );
console.log( y );
zmap.ndarray( x.length, x, 1, 0, y, -1, y.length-1, scale );
console.log( y );
```
</section>
<!-- /.examples -->
<!-- C interface documentation. -->
* * *
<section class="c">
## C APIs
<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
<section class="intro">
</section>
<!-- /.intro -->
<!-- C usage documentation. -->
<section class="usage">
### Usage
```c
#include "stdlib/strided/base/zmap.h"
```
#### stdlib_strided_zmap( N, \*X, strideX, \*Y, strideY, fcn )
Applies a unary function to a double-precision complex floating-point strided input array and assigns results to a double-precision complex floating-point strided output array.
```c
#include <stdint.h>
#include <complex.h>
static double complex scale( const double complex x ) {
double re = creal( x );
double im = cimag( x );
return ( re+10.0 ) + ( im+10.0 )*I;
}
double complex X[] = { 1.0+1.0*I, 2.0+2.0*I, 3.0+3.0*I, 4.0+4.0*I, 5.0+5.0*I, 6.0+6.0*I };
double complex Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
int64_t N = 6;
stdlib_strided_zmap( N, X, 1, Y, 1, scale );
```
The function accepts the following arguments:
- **N**: `[in] int64_t` number of indexed elements.
- **X**: `[in] double complex*` input array.
- **strideX** `[in] int64_t` index increment for `X`.
- **Y**: `[out] double complex*` output array.
- **strideY**: `[in] int64_t` index increment for `Y`.
- **fcn**: `[in] double complex (*fcn)( double complex )` unary function to apply.
```c
void stdlib_strided_zmap( const int64_t N, const double complex *X, const int64_t strideX, double complex *Y, const int64_t strideY, double complex (*fcn)( double complex ) );
```
</section>
<!-- /.usage -->
<!-- C API usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
<section class="notes">
</section>
<!-- /.notes -->
<!-- C API usage examples. -->
<section class="examples">
### Examples
```c
#include "stdlib/strided/base/zmap.h"
#include <stdint.h>
#include <stdio.h>
#include <inttypes.h>
#include <complex.h>
// Define a callback:
static double complex scale( const double complex x ) {
double re = creal( x );
double im = cimag( x );
return ( re+10.0 ) + ( im+10.0 )*I;
}
int main( void ) {
// Create an input strided array:
double complex X[] = { 1.0+1.0*I, 2.0+2.0*I, 3.0+3.0*I, 4.0+4.0*I, 5.0+5.0*I, 6.0+6.0*I };
// Create an output strided array:
double complex Y[] = { 0.0, 0.0, 0.0, 0.0, 0.0, 0.0 };
// Specify the number of elements:
int64_t N = 6;
// Define the strides:
int64_t strideX = 1;
int64_t strideY = -1;
// Apply the callback:
stdlib_strided_zmap( N, X, strideX, Y, strideY, scale );
// Print the results:
for ( int64_t i = 0; i < N; i++ ) {
printf( "Y[ %"PRId64" ] = %lf + %lfi\n", i, creal( Y[i] ), cimag( Y[i] ) );
}
}
```
</section>
<!-- /.examples -->
</section>
<!-- /.c -->
<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
<section class="related">
* * *
## See Also
- <span class="package-name">[`@stdlib/strided/base/cmap`][@stdlib/strided/base/cmap]</span><span class="delimiter">: </span><span class="description">apply a unary function to a single-precision complex floating-point strided input array and assign results to a single-precision complex floating-point strided output array.</span>
- <span class="package-name">[`@stdlib/strided/base/unary`][@stdlib/strided/base/unary]</span><span class="delimiter">: </span><span class="description">apply a unary callback to elements in a strided input array and assign results to elements in a strided output array.</span>
</section>
<!-- /.related -->
<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
<section class="links">
[@stdlib/array/complex128]: https://www.npmjs.com/package/@stdlib/array-complex128
<!-- <related-links> -->
[@stdlib/strided/base/cmap]: https://github.com/stdlib-js/strided/tree/main/base/cmap
[@stdlib/strided/base/unary]: https://github.com/stdlib-js/strided/tree/main/base/unary
<!-- </related-links> -->
</section>
<!-- /.links -->