npm package: @stdlib/stats-base-ndarray-nanmax-by
Description: Compute the maximum value of a one-dimensional ndarray via a callback function, ignoring NaN values.
Author: The Stdlib Authors
Latest version: 0.1.1

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# nanmaxBy

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> Compute the maximum value of a one-dimensional ndarray via a callback function, ignoring `NaN` values.

<section class="intro">

</section>

<!-- /.intro -->

<section class="installation">

## Installation

```bash
npm install @stdlib/stats-base-ndarray-nanmax-by
```

</section>

<section class="usage">

## Usage

```javascript
var nanmaxBy = require( '@stdlib/stats-base-ndarray-nanmax-by' );
```

#### nanmaxBy( arrays, clbk\[, thisArg ] )

Computes the maximum value of a one-dimensional ndarray via a callback function, ignoring `NaN` values.

```javascript
var ndarray = require( '@stdlib/ndarray-base-ctor' );

function clbk( value ) {
    return value * 2.0;
}

var xbuf = [ 1.0, NaN, 4.0, 2.0 ];
var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );

var v = nanmaxBy( [ x ], clbk );
// returns 8.0
```

The function has the following parameters:

-   **arrays**: array-like object containing a one-dimensional input ndarray.
-   **clbk**: callback function.
-   **thisArg**: callback execution context (_optional_).

The invoked callback is provided three arguments:

-   **value**: current array element.
-   **idx**: current array element index.
-   **array**: input ndarray.

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

```javascript
var ndarray = require( '@stdlib/ndarray-base-ctor' );

function clbk( value ) {
    this.count += 1;
    return value * 2.0;
}

var xbuf = [ 1.0, 3.0, NaN, 2.0 ];
var x = new ndarray( 'generic', xbuf, [ 4 ], [ 1 ], 0, 'row-major' );
var ctx = {
    'count': 0
};

var v = nanmaxBy( [ x ], clbk, ctx );
// returns 6.0

var count = ctx.count;
// returns 4
```

</section>

<!-- /.usage -->

<section class="notes">

## Notes

-   If provided an empty one-dimensional ndarray, the function returns `NaN`.
-   A provided callback function should return a numeric value.
-   If a provided callback function returns `NaN`, the value is ignored.
-   If a provided callback function does not return any value (or equivalently, explicitly returns `undefined`), the value is **ignored**.

</section>

<!-- /.notes -->

<section class="examples">

## Examples

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

```javascript
var uniform = require( '@stdlib/random-base-uniform' );
var bernoulli = require( '@stdlib/random-base-bernoulli' );
var filledarrayBy = require( '@stdlib/array-filled-by' );
var ndarray = require( '@stdlib/ndarray-base-ctor' );
var ndarray2array = require( '@stdlib/ndarray-to-array' );
var nanmaxBy = require( '@stdlib/stats-base-ndarray-nanmax-by' );

function clbk( value ) {
    return value * 2.0;
}

function rand() {
    if ( bernoulli( 0.8 ) < 1 ) {
        return NaN;
    }
    return uniform( -50.0, 50.0 );
}

var xbuf = filledarrayBy( 10, 'generic', rand );
var x = new ndarray( 'generic', xbuf, [ xbuf.length ], [ 1 ], 0, 'row-major' );
console.log( ndarray2array( x ) );

var v = nanmaxBy( [ x ], clbk );
console.log( v );
```

</section>

<!-- /.examples -->

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<section class="related">

</section>

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* * *

## Notice

This package is part of [stdlib][stdlib], a standard library for JavaScript and Node.js, with an emphasis on numerical and scientific computing. The library provides a collection of robust, high performance libraries for mathematics, statistics, streams, utilities, and more.

For more information on the project, filing bug reports and feature requests, and guidance on how to develop [stdlib][stdlib], see the main project [repository][stdlib].

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---

## License

See [LICENSE][stdlib-license].


## Copyright

Copyright &copy; 2016-2026. The Stdlib [Authors][stdlib-authors].

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