feat: add stats/array/stdev

lib/node_modules/@stdlib/stats/array/stdev/README.md

@@ -0,0 +1,121 @@
+<!--
+
+@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.
+
+-->
+
+# stdev
+
+> Calculate the [standard deviation][standard-deviation] of an array.
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var stdev = require( '@stdlib/stats/array/stdev' );
+```
+
+#### stdev( x\[, correction] )
+
+Computes the [standard deviation][standard-deviation] of an array.
+
+```javascript
+var x = [ 1.0, -2.0, 2.0 ];
+
+var v = stdev( x );
+// returns ~2.0817
+```
+
+The function has the following parameters:
+
+-   **x**: input array.
+-   **correction**: degrees of freedom adjustment. Setting this parameter to a value other than `0` has the effect of adjusting the divisor during the calculation of the [standard deviation][standard-deviation] according to `N-c` where `N` corresponds to the number of array elements and `c` corresponds to the provided degrees of freedom adjustment. When computing the [standard deviation][standard-deviation] of a population, setting this parameter to `0` is the standard choice (i.e., the provided array contains data constituting an entire population). When computing the unbiased sample [standard deviation][standard-deviation], setting this parameter to `1` is the standard choice (i.e., the provided array contains data sampled from a larger population; this is commonly referred to as Bessel's correction). Default: `1.0`.
+
+By default, the function computes the sample [standard deviation][standard-deviation]. To use adjust the degrees of freedom when computing the [standard deviation][standard-deviation], provide a `correction` argument.
+
+```javascript
+var x = [ 1.0, -2.0, 2.0 ];
+
+var v = stdev( x, 0.0 );
+// returns ~1.6997
+```
+
+</section>
+
+<!-- /.usage -->
+
+<section class="notes">
+
+## Notes
+
+-   If provided an empty array, the function returns `NaN`.
+-   If `N - c` is less than or equal to `0` (where `c` corresponds to the provided degrees of freedom adjustment), both functions return `NaN`.
+-   The function supports array-like objects having getter and setter accessors for array element access (e.g., [`@stdlib/array/base/accessor`][@stdlib/array/base/accessor]).
+
+</section>
+
+<!-- /.notes -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
+var stdev = require( '@stdlib/stats/array/stdev' );
+
+var x = discreteUniform( 10, -50, 50, {
+    'dtype': 'float64'
+});
+console.log( x );
+
+var v = stdev( x );
+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">
+
+[standard-deviation]: https://en.wikipedia.org/wiki/Standard_deviation
+
+[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
+
+</section>
+
+<!-- /.links -->

lib/node_modules/@stdlib/stats/array/stdev/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 pkg = require( './../package.json' ).name;
+var stdev = require( './../lib' );
+
+
+// VARIABLES //
+
+var options = {
+	'dtype': 'generic'
+};
+
+
+// FUNCTIONS //
+
+/**
+* Creates 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 = stdev( x, 1.0 );
+			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 //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+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( pkg+':len='+len, f );
+	}
+}
+
+main();

lib/node_modules/@stdlib/stats/array/stdev/docs/repl.txt

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+
+{{alias}}( x[, correction] )
+    Computes the standard deviation of an array.
+
+    If provided an empty array, the function returns `NaN`.
+
+    Parameters
+    ----------
+    x: Array<number>|TypedArray
+        Input array.
+
+    correction: number (optional)
+        Degrees of freedom adjustment. Setting this parameter to a value other
+        than `0` has the effect of adjusting the divisor during the calculation
+        of the standard deviation according to `N-c` where `N` corresponds to
+        the number of array elements and `c` corresponds to the provided
+        degrees of freedom adjustment. When computing the standard deviation of
+        a population, setting this parameter to `0` is the standard choice
+        (i.e., the provided array contains data constituting an entire
+        population). When computing the unbiased sample standard deviation,
+        setting this parameter to `1` is the standard choice (i.e., the
+        provided array contains data sampled from a larger population; this is
+        commonly referred to as Bessel's correction). Default: `1.0`.
+
+    Returns
+    -------
+    out: number
+        The standard deviation.
+
+    Examples
+    --------
+    > var x = [ 1.0, -2.0, 2.0 ];
+    > {{alias}}( x, 1.0 )
+    ~2.0817
+
+    See Also
+    --------
+

lib/node_modules/@stdlib/stats/array/stdev/docs/types/index.d.ts

@@ -0,0 +1,48 @@
+/*
+* @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"/>
+
+import { NumericArray, Collection, AccessorArrayLike } from '@stdlib/types/array';
+
+/**
+* Input array.
+*/
+type InputArray = NumericArray | Collection<number> | AccessorArrayLike<number>;
+
+/**
+* Computes the standard deviation of an array.
+*
+* @param x - input array
+* @param correction - degrees of freedom adjustment
+* @returns standard deviation
+*
+* @example
+* var x = [ 1.0, -2.0, 2.0 ];
+*
+* var v = stdev( x, 1.0 );
+* // returns ~2.0817
+*/
+declare function stdev( x: InputArray, correction?: number ): number;
+
+
+// EXPORTS //
+
+export = stdev;

lib/node_modules/@stdlib/stats/array/stdev/docs/types/test.ts

@@ -0,0 +1,76 @@
+/*
+* @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.
+*/
+
+import AccessorArray = require( '@stdlib/array/base/accessor' );
+import stdev = require( './index' );
+
+
+// TESTS //
+
+// The function returns a number...
+{
+	const x = new Float64Array( 10 );
+
+	stdev( x ); // $ExpectType number
+	stdev( new AccessorArray( x ) ); // $ExpectType number
+
+	stdev( x, 1.0 ); // $ExpectType number
+	stdev( new AccessorArray( x ), 1.0 ); // $ExpectType number
+}
+
+// The compiler throws an error if the function is provided a first argument which is not a numeric array...
+{
+	stdev( 10 ); // $ExpectError
+	stdev( '10' ); // $ExpectError
+	stdev( true ); // $ExpectError
+	stdev( false ); // $ExpectError
+	stdev( null ); // $ExpectError
+	stdev( undefined ); // $ExpectError
+	stdev( {} ); // $ExpectError
+	stdev( ( x: number ): number => x ); // $ExpectError
+
+	stdev( 10, 1.0 ); // $ExpectError
+	stdev( '10', 1.0 ); // $ExpectError
+	stdev( true, 1.0 ); // $ExpectError
+	stdev( false, 1.0 ); // $ExpectError
+	stdev( null, 1.0 ); // $ExpectError
+	stdev( undefined, 1.0 ); // $ExpectError
+	stdev( {}, 1.0 ); // $ExpectError
+	stdev( ( x: number ): number => x, 1.0 ); // $ExpectError
+}
+
+// The compiler throws an error if the function is provided a second argument which is not a number...
+{
+	const x = new Float64Array( 10 );
+
+	stdev( x, '10' ); // $ExpectError
+	stdev( x, true ); // $ExpectError
+	stdev( x, false ); // $ExpectError
+	stdev( x, null ); // $ExpectError
+	stdev( x, [] ); // $ExpectError
+	stdev( x, {} ); // $ExpectError
+	stdev( x, ( x: number ): number => x ); // $ExpectError
+}
+
+// The compiler throws an error if the function is provided an unsupported number of arguments...
+{
+	const x = new Float64Array( 10 );
+
+	stdev(); // $ExpectError
+	stdev( x, 1.0, {} ); // $ExpectError
+}