8000 feat: add `stats/strided/midrange-by` by Orthodox-64 · Pull Request #9328 · stdlib-js/stdlib · GitHub
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feat: add stats/strided/midrange-by #9328

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6c83a27
feat: add stats/strided/midrange-by
Orthodox-64 Dec 23, 2025
93c9c66
fix: lint
Orthodox-64 Dec 23, 2025
9c6c904
fixed lint
Orthodox-64 Dec 23, 2025
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230 changes: 230 additions & 0 deletions lib/node_modules/@stdlib/stats/strided/midrange-by/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.

-->

# midrangeBy

> Calculate the [mid-range][mid-range] of a strided array via a callback function.

<section class="intro">

The [**mid-range**][mid-range], or **mid-extreme**, is the arithmetic mean of the maximum and minimum values in a data set. The measure is the midpoint of the range and a measure of central tendency.

</section>

<!-- /.intro -->

<section class="usage">

## Usage

```javascript
var midrangeBy = require( '@stdlib/stats/strided/midrange-by' );
```

#### midrangeBy( N, x, strideX, clbk\[, thisArg] )

Computes the [mid-range][mid-range] of a strided array via a callback function.

```javascript
function accessor( v ) {
return v * 2.0;
}

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

var v = midrangeBy( x.length, x, 1, accessor );
// returns -1.0
```

The function has the following parameters:

- **N**: number of indexed elements.
- **x**: input [`Array`][mdn-array], [`typed array`][mdn-typed-array], or an array-like object (excluding strings and functions).
- **strideX**: stride length.
- **clbk**: callback function.
- **thisArg**: execution context (_optional_).

The invoked callback is provided four arguments:

- **value**: array element.
- **aidx**: array index.
- **sidx**: strided index (`offset + aidx*stride`).
- **array**: input array/collection.

To set the callback execution context, provide a `thisArg`.

```javascript
function accessor( v ) {
this.count += 1;
return v * 2.0;
}

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

var context = {
'count': 0
};

var v = midrangeBy( x.length, x, 1, accessor, context );
// returns -1.0

var cnt = context.count;
// returns 8
```

The `N` and stride parameters determine which elements in the strided array are accessed at runtime. For example, to access every other element

```javascript
function accessor( v ) {
return v * 2.0;
}

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

var v = midrangeBy( 4, x, 2, accessor );
// returns 2.0
```

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' );

function accessor( v ) {
return v * 2.0;
}

// 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

// Access every other element...
var v = midrangeBy( 3, x1, 2, accessor );
// returns -8.0
```

#### midrangeBy.ndarray( N, x, strideX, offsetX, clbk\[, thisArg] )

Computes the [mid-range][mid-range] of a strided array via a callback function and using alternative indexing semantics.

```javascript
function accessor( v ) {
return v * 2.0;
}

var x = [ -2.0, 1.0, 3.0, -5.0, 4.0, 0.0, -1.0, -3.0 ];

var v = midrangeBy.ndarray( x.length, x, 1, 0, accessor );
// returns -1.0
```

The function has the following additional parameters:

- **offsetX**: 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 `x`

```javascript
function accessor( v ) {
return v * 2.0;
}

var x = [ 1.0, -2.0, 3.0, -4.0, 5.0, -6.0 ];

var v = midrangeBy.ndarray( 3, x, 1, x.length-3, accessor );
// returns -1.0
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

- If `N <= 0`, both functions return `NaN`.
- A provided callback function should return a numeric value.
- If a provided callback function does not return any value (or equivalently, explicitly returns `undefined`), the value is **ignored**.
- Both functions support array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).
- When possible, prefer using [`midrange`][@stdlib/stats/strided/midrange], as, depending on the environment, it is likely to be significantly more performant.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

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

function accessor( v ) {
return v * 2.0;
}

var x = discreteUniform( 10, -50, 50, {
'dtype': 'float64'
});
console.log( x );

var v = midrangeBy( x.length, x, 1, accessor );
console.log( v );
```

</section>

<!-- /.examples -->

<!-- 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">

[mid-range]: https://en.wikipedia.org/wiki/Mid-range

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

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

[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor

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

[@stdlib/stats/strided/midrange]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/strided/midrange

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

</section>

<!-- /.links -->
103 changes: 103 additions & 0 deletions lib/node_modules/@stdlib/stats/strided/midrange-by/benchmark/benchmark.js
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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.
*/

'use strict';

// MODULES //

var bench = require( '@stdlib/bench' );
var uniform = require( '@stdlib/random/array/uniform' );
var isnan = require( '@stdlib/math/base/assert/is-nan' );
var pow = require( '@stdlib/math/base/special/pow' );
var format = require( '@stdlib/string/format' );
var pkg = require( './../package.json' ).name;
var midrangeBy = require( './../lib/main.js' );


// VARIABLES //

var options = {
'dtype': 'generic'
};


// FUNCTIONS //

/**
* Accessor function.
*
* @private
* @param {number} value - array element
* @returns {number} accessed value
*/
function accessor( value ) {
return value * 2.0;
}

/**
* Create a benchmark function.
*
* @private
* @param {PositiveInteger} len - array length
* @returns {Function} benchmark function
*/
function createBenchmark( len ) {
var x = uniform( len, -10, 10, options );
return benchmark;

function benchmark( b ) {
var v;
var i;

b.tic();
for ( i = 0; i < b.iterations; i++ ) {
v = midrangeBy( x.length, x, 1, accessor );
if ( isnan( v ) ) {
b.fail( 'should not return NaN' );
}
}
b.toc();
if ( isnan( v ) ) {
b.fail( 'should not return NaN' );
}
b.pass( 'benchmark finished' );
b.end();
}
}


// MAIN //

function main() {
var len;
var min;
var max;
var f;
var i;

min = 1; // 10^min
max = 6; // 10^max

for ( i = min; i <= max; i++ ) {
len = pow( 10, i );
f = createBenchmark( len );
bench( format( '%s:len=%d', pkg, len ), f );
}
}

main();
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