[Add]: Create new package stats/incr/nanwmean to handle NaN values

lib/node_modules/@stdlib/stats/incr/nanwmean/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.
+
+-->
+
+# incrnanwmean
+
+> Compute a [weighted arithmetic mean][weighted-arithmetic-mean] incrementally, ignoring `NaN` values.
+
+<section class="intro">
+
+The [weighted arithmetic mean][weighted-arithmetic-mean] is defined as
+
+<!-- <equation class="equation" label="eq:weighted_arithmetic_mean_nan" align="center" raw="\bar{x} = \frac{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i} x_{i}}{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i}}" alt="Equation for the weighted arithmetic mean ignoring NaNs."> -->
+
+```math
+\bar{x} = \frac{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i} x_{i}}{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i}}
+```
+<!-- <div class="equation" align="center" data-raw-text="\bar{x} = \frac{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i} x_{i}}{\displaystyle\sum_{i=0, x_i \neq \text{NaN}}^{n-1} w_{i}}" data-equation="eq:weighted_arithmetic_mean_nan">
+    <img src="docs/img/equation_weighted_arithmetic_mean_nan.svg" alt="Equation for the weighted arithmetic mean ignoring NaNs.">
+    <br>
+</div> -->
+
+<!-- </equation> -->
+
+</section>
+
+
+<!-- /.intro -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var incrnanwmean = require( '@stdlib/stats/incr/nanwmean' );
+```
+
+#### incrnanwmean()
+
+Returns an accumulator `function` which incrementally computes a [weighted arithmetic mean][weighted-arithmetic-mean], ignoring `NaN` values.
+
+```javascript
+var accumulator = incrnanwmean();
+```
+
+#### accumulator( \[x, w] )
+
+If provided an input value `x` and a weight `w`, the accumulator function returns an updated weighted mean while ignoring `NaN` values. If not provided any input values, the accumulator function returns the current mean.
+
+```javascript
+var accumulator = incrnanwmean();
+
+var mu = accumulator();
+// returns null
+
+mu = accumulator( 2.0, 1.0 );
+// returns 2.0
+
+mu = accumulator( 2.0, 0.5 );
+// returns 2.0
+
+mu = accumulator( 3.0, 1.5 );
+// returns 2.5
+
+mu = accumulator();
+// returns 2.5
+```
+
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   Input values are **not** type checked. If provided `NaN` for the value `x`, the accumulator **ignores** it and does not update the weighted mean. If provided `NaN` for the weight `w`, the corresponding value is ignored. If non-numeric inputs are possible, you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
+
+</section>
+
+<!-- /.notes -->
+
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var randu = require( '@stdlib/random/base/randu' );
+var incrnanwmean = require( '@stdlib/stats/incr/nanwmean' );
+
+var accumulator;
+var v;
+var w;
+var i;
+
+accumulator = incrnanwmean();
+
+for ( i = 0; i < 100; i++ ) {
+    v = ( randu() < 0.1 ) ? NaN : randu() * 100.0; // Introduce NaNs randomly
+    w = ( randu() < 0.1 ) ? NaN : randu() * 100.0; // Introduce NaNs randomly
+    accumulator( v, w );
+}
+console.log( accumulator() );
+```
+
+</section>

lib/node_modules/@stdlib/stats/incr/nanwmean/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 randu = require( '@stdlib/random/base/randu' );
+var pkg = require( './../package.json' ).name;
+var incrnanwmean = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var f;
+	var i;
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		f = incrnanwmean();
+		if ( typeof f !== 'function' ) {
+			b.fail( 'should return a function' );
+		}
+	}
+	b.toc();
+	if ( typeof f !== 'function' ) {
+		b.fail( 'should return a function' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});
+
+bench( pkg+'::accumulator', function benchmark( b ) {
+	var acc;
+	var v;
+	var i;
+
+	acc = incrnanwmean();
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		v = acc( randu(), 1.0 );
+		if ( v !== v ) {
+			b.fail( 'should not return NaN' );
+		}
+	}
+	b.toc();
+	if ( v !== v ) {
+		b.fail( 'should not return NaN' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});

lib/node_modules/@stdlib/stats/incr/nanwmean/docs/repl.txt

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+{{alias}}()
+    Returns an accumulator function which incrementally computes a weighted
+    arithmetic mean while ignoring NaN values.
+
+    If provided arguments, the accumulator function returns an updated weighted
+    mean. If not provided arguments, the accumulator function returns the
+    current weighted mean.
+
+    If `x` is `NaN`, the function ignores it and does not update the mean.
+    If `w` is `NaN` or less than or equal to zero, the function ignores the input.
+    If all values provided are `NaN`, the accumulated value remains `null`.
+
+    The accumulator function accepts two arguments:
+
+    - x: value.
+    - w: weight.
+
+    Returns
+    -------
+    acc: Function
+        Accumulator function.
+
+    Examples
+    --------
+    > var accumulator = {{alias}}();
+    > var mean = accumulator()
+    null
+    > mean = accumulator(2.0, 3.0)
+    2.0
+    > mean = accumulator(NaN, 4.0)
+    2.0  (NaN value is ignored)
+    > mean = accumulator(3.0, NaN)
+    2.0  (NaN weight is ignored)
+    > mean = accumulator(5.0, 2.0)
+    3.5
+    > mean = accumulator()
+    3.5
+
+    See Also
+    --------

lib/node_modules/@stdlib/stats/incr/nanwmean/docs/types/index.d.ts

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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.
+*/
+
+// TypeScript Version: 4.1
+
+/// <reference types="@stdlib/types"/>
+
+/**
+* If provided both arguments, returns an updated weighted arithmetic mean while ignoring NaN values; otherwise, returns the current weighted arithmetic mean.
+*
+* ## Notes
+*
+* -   If `x` is `NaN`, the function ignores it and does not update the mean.
+* -   If `w` is `NaN` or less than or equal to zero, the function ignores the input.
+* -   If all values provided are `NaN`, the accumulated value remains `null`.
+*
+* @param x - value
+* @param w - weight
+* @returns weighted arithmetic mean (ignoring NaN values)
+*/
+type accumulator = ( x?: number, w?: number ) => number | null;
+
+/**
+* Returns an accumulator function which incrementally computes a weighted arithmetic mean while ignoring NaN values.
+*
+* @returns accumulator function
+*
+* @example
+* var incrnanwmean = require('@stdlib/stats/incr/nanwmean');
+ * 
+ * var accumulator = incrnanwmean();
+ * 
+ * var mean = accumulator();
+ * // returns null
+ * 
+ * mean = accumulator(2.0, 3.0);
+ * // returns 2.0
+ * 
+ * mean = accumulator(NaN, 4.0);
+ * // returns 2.0 (Skips NaN)
+ * 
+ * mean = accumulator(3.0 , NaN);
+ * // returns 2.0 (Skips NaN)
+ * 
+ * mean = accumulator(5.0, 2.0);
+ * // returns 3.5
+ * 
+ * mean = accumulator();
+ * // returns 3.5
+*/
+declare function incrnanwmean(): accumulator;
+
+// EXPORTS //
+
+export = incrnanwmean;

lib/node_modules/@stdlib/stats/incr/nanwmean/docs/types/test.ts

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+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2019 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.
+*/
+
+import incrnanwmean = require( './index' );
+
+// TESTS //
+
+// The function returns an accumulator function...
+{
+	incrnanwmean(); // $ExpectType accumulator
+}
+
+// The compiler throws an error if the function is provided arguments...
+{
+	incrnanwmean( '5' ); // $ExpectError
+	incrnanwmean( 5 ); // $ExpectError
+	incrnanwmean( true ); // $ExpectError
+	incrnanwmean( false ); // $ExpectError
+	incrnanwmean( null ); // $ExpectError
+	incrnanwmean( undefined ); // $ExpectError
+	incrnanwmean( [] ); // $ExpectError
+	incrnanwmean( {} ); // $ExpectError
+	incrnanwmean( ( x: number ): number => x ); // $ExpectError
+}
+
+// The function returns an accumulator function which returns an accumulated result...
+{
+	const acc = incrnanwmean();
+
+	acc(); // $ExpectType number | null
+	acc( 3.14, 1.0 ); // $ExpectType number | null
+	acc( NaN, 2.0 ); // $ExpectType number | null
+	acc( 4.5, NaN ); // $ExpectType number | null
+}
+
+// The compiler throws an error if the returned accumulator function is provided invalid arguments...
+{
+	const acc = incrnanwmean();
+
+	acc( '5', 1.0 ); // $ExpectError
+	acc( true, 1.0 ); // $ExpectError
+	acc( false, 1.0 ); // $ExpectError
+	acc( null, 1.0 ); // $ExpectError
+	acc( [], 1.0 ); // $ExpectError
+	acc( {}, 1.0 ); // $ExpectError
+	acc( ( x: number ): number => x, 1.0 ); // $ExpectError
+
+	acc( 3.14, '5' ); // $ExpectError
+	acc( 3.14, true ); // $ExpectError
+	acc( 3.14, false ); // $ExpectError
+	acc( 3.14, null ); // $ExpectError
+	acc( 3.14, [] ); // $ExpectError
+	acc( 3.14, {} ); // $ExpectError
+	acc( 3.14, ( x: number ): number => x ); // $ExpectError
+}