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339 changes: 339 additions & 0 deletions lib/node_modules/@stdlib/stats/strided/distances/deuclidean/README.md
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<!--

@license Apache-2.0

Copyright (c) 2025 The Stdlib Authors.

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.

-->

# deuclidean

> Compute the euclidean distance between two double-precision floating-point strided arrays.

<section class="intro">

The [euclidean distance][wikipedia-euclidean-distance] is defined as

<!-- <equation class="equation" label="eq:euclidean_distance" align="center" raw="d = \sqrt{\sum_{i=0}^{N-1} (y_i - x_i)^2}" alt="Equation for the euclidean distance."> -->

```math
d = \sqrt{\sum_{i=0}^{N-1} (y_i - x_i)^2}
```

<!-- <div class="equation" align="center" data-raw-text="d = \sqrt{\sum_{i=0}^{N-1} (y_i - x_i)^2}" data-equation="eq:euclidean_distance">
<img src="" alt="Euclidean distance.">
<br>
</div> -->

<!-- </equation> -->

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var deuclidean = require( '@stdlib/stats/strided/distances/deuclidean' );
```

#### deuclidean( N, x, strideX, y, strideY )

Computes the euclidean distance between two double-precision floating-point strided arrays.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var y = new Float64Array( [ 2.0, 1.0, 2.0, 1.0, -2.0, 2.0, 3.0, 4.0 ] );

var z = deuclidean( x.length, x, 1, y, 1 );
// returns ~8.485
```

The function has the following parameters:

- **N**: number of indexed elements.
- **x**: input [`Float64Array`][@stdlib/array/float64].
- **strideX**: stride length of `x`.
- **y**: input [`Float64Array`][@stdlib/array/float64].
- **strideY**: stride length of `y`.

The `N` and stride parameters determine which elements in the strided arrays are accessed at runtime. For example, to calculate the euclidean distance between every other value in `x` and the first `N` elements of `y` in reverse order,

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 1.0, 1.0, 1.0, 1.0, 1.0, 1.0 ] );

var z = deuclidean( 3, x, 2, y, -1 );
// returns ~4.472
```

Note that indexing is relative to the first index. To introduce an offset, use [`typed array`][mdn-typed-array] views.

<!-- eslint-disable stdlib/capitalized-comments -->

```javascript
var Float64Array = require( '@stdlib/array/float64' );

// Initial arrays...
var x0 = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y0 = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

// 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 z = deuclidean( 3, x1, 1, y1, 1 );
// returns ~13.856
```

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

Computes the euclidean distance between two double-precision floating-point strided arrays using alternative indexing semantics.

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 ] );
var y = new Float64Array( [ 2.0, 1.0, 2.0, 1.0, -2.0, 2.0, 3.0, 4.0 ] );

var z = deuclidean.ndarray( x.length, x, 1, 0, y, 1, 0 );
// returns ~8.485
```

The function has the following additional parameters:

- **offsetX**: starting index for `x`.
- **offsetY**: starting index for `y`.

While [`typed array`][mdn-typed-array] views mandate a view offset based on the underlying buffer, the offset parameters support indexing semantics based on starting indices. For example, to calculate the euclidean distance between every other value in `x` starting from the second value with the last 3 elements in `y` in reverse order

```javascript
var Float64Array = require( '@stdlib/array/float64' );

var x = new Float64Array( [ 1.0, 2.0, 3.0, 4.0, 5.0, 6.0 ] );
var y = new Float64Array( [ 7.0, 8.0, 9.0, 10.0, 11.0, 12.0 ] );

var z = deuclidean.ndarray( 3, x, 2, 1, y, -1, y.length-1 );
// returns ~12.845
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

- If `N <= 0`, both functions return `0.0`.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

<!-- eslint no-undef: "error" -->

```javascript
var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
var deuclidean = require( '@stdlib/stats/strided/distances/deuclidean' );

var opts = {
'dtype': 'float64'
};
var x = discreteUniform( 10, 0, 100, opts );
console.log( x );

var y = discreteUniform( x.length, 0, 10, opts );
console.log( y );

var out = deuclidean.ndarray( x.length, x, 1, 0, y, -1, y.length-1 );
console.log( out );
```

</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/stats/strided/distances/deuclidean.h"
```

#### stdlib_strided_deuclidean( N, \*X, strideX, \*Y, strideY )

Computes the euclidean distance between two double-precision floating-point strided arrays.

```c
const double x[] = { 1.0, 2.0, 2.0, -7.0, -2.0, 3.0, 4.0, 2.0 };
const double y[] = { 2.0, 1.0, 2.0, 1.0, -2.0, 2.0, 3.0, 4.0 };

double v = stdlib_strided_deuclidean( 8, x, 1, y, 1 );
// returns ~8.485
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **X**: `[in] double*` first input array.
- **strideX**: `[in] CBLAS_INT` stride length of `X`.
- **Y**: `[in] double*` second input array.
- **strideY**: `[in] CBLAS_INT` stride length of `Y`.

```c
double stdlib_strided_deuclidean( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const double *Y, const CBLAS_INT strideY );
```

<!--lint disable maximum-heading-length-->

#### stdlib_strided_deuclidean_ndarray( N, \*X, strideX, offsetX, \*Y, strideY, offsetY )

<!--lint enable maximum-heading-length-->

Computes the euclidean distance between two double-precision floating-point strided arrays using alternative indexing semantics.

```c
const double x[] = { 4.0, 2.0, -3.0, 5.0, -1.0 };
const double y[] = { 2.0, 6.0, -1.0, -4.0, 8.0 };

double v = stdlib_strided_deuclidean_ndarray( 5, x, -1, 4, y, -1, 4 );
// returns ~13.638
```

The function accepts the following arguments:

- **N**: `[in] CBLAS_INT` number of indexed elements.
- **X**: `[in] double*` first input array.
- **strideX**: `[in] CBLAS_INT` stride length of `X`.
- **offsetX**: `[in] CBLAS_INT` starting index for `X`.
- **Y**: `[in] double*` second input array.
- **strideY**: `[in] CBLAS_INT` stride length of `Y`.
- **offsetY**: `[in] CBLAS_INT` starting index for `Y`.

```c
double stdlib_strided_deuclidean_ndarray( const CBLAS_INT N, const double *X, const CBLAS_INT strideX, const CBLAS_INT offsetX, const double *Y, const CBLAS_INT strideY, const CBLAS_INT offsetY );
```

</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/stats/strided/distances/deuclidean.h"
#include <stdio.h>

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

// Specify the number of elements:
const int N = 8;

// Specify strides:
const int strideX = 1;
const int strideY = -1;

// Compute the euclidean distance between `x` and `y`:
double sim = stdlib_strided_deuclidean( N, x, strideX, y, strideY );

// Print the result:
printf( "euclidean distance: %lf\n", sim );

// Compute the euclidean distance between `x` and `y` with offsets:
sim = stdlib_strided_deuclidean_ndarray( N, x, strideX, 0, y, strideY, N-1 );

// Print the result:
printf( "euclidean distance: %lf\n", sim );
}
```

</section>

<!-- /.examples -->

</section>

<!-- /.c -->

<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->

<section class="related">

</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/float64]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/float64

[mdn-typed-array]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypedArray

[wikipedia-euclidean-distance]: https://en.wikipedia.org/wiki/Euclidean_distance

<!-- <related-links> -->

<!-- </related-links> -->

</section>

<!-- /.links -->
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