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feat: add stats/array/stdevpn
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‎lib/node_modules/@stdlib/stats/array/stdevpn/README.md

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<!--
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@license Apache-2.0
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Copyright (c) 2025 The Stdlib Authors.
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Licensed under the Apache License, Version 2.0 (the "License");
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you may not use this file except in compliance with the License.
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You may obtain a copy of the License at
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http://www.apache.org/licenses/LICENSE-2.0
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Unless required by applicable law or agreed to in writing, software
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distributed under the License is distributed on an "AS IS" BASIS,
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WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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See the License for the specific language governing permissions and
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limitations under the License.
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-->
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# stdevpn
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> Calculate the [standard deviation][standard-deviation] of an array using a two-pass algorithm.
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<section class="intro">
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</section>
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<!-- /.intro -->
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<section class="usage">
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## Usage
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```javascript
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var stdevpn = require( '@stdlib/stats/array/stdevpn' );
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```
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#### stdevpn( x\[, correction] )
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Computes the [standard deviation][standard-deviation] of an array using a two-pass algorithm.
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```javascript
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var x = [ 1.0, -2.0, 2.0 ];
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var v = stdevpn( x );
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// returns ~2.0817
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```
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The function has the following parameters:
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- **x**: input array.
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- **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`.
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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.
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```javascript
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var x = [ 1.0, -2.0, 2.0 ];
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var v = stdevpn( x, 0.0 );
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// returns ~1.6997
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```
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</section>
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<!-- /.usage -->
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<section class="notes">
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## Notes
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- If provided an empty array, the function returns `NaN`.
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- If `N - c` is less than or equal to `0` (where `c` corresponds to the provided degrees of freedom adjustment), both functions return `NaN`.
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- 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]).
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</section>
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<!-- /.notes -->
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<section class="examples">
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## Examples
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<!-- eslint no-undef: "error" -->
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```javascript
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var discreteUniform = require( '@stdlib/random/array/discrete-uniform' );
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var stdevpn = require( '@stdlib/stats/array/stdevpn' );
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var x = discreteUniform( 10, -50, 50, {
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'dtype': 'float64'
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});
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console.log( x );
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var v = stdevpn( x );
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console.log( v );
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```
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</section>
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<!-- /.examples -->
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<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
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<section class="related">
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</section>
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<!-- /.related -->
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<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
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<section class="links">
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[standard-deviation]: https://en.wikipedia.org/wiki/Standard_deviation
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[@stdlib/array/base/accessor]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/accessor
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</section>
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<!-- /.links -->

‎lib/node_modules/@stdlib/stats/array/stdevpn/benchmark/benchmark.js

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/**
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var bench = require( '@stdlib/bench' );
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var uniform = require( '@stdlib/random/array/uniform' );
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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var pow = require( '@stdlib/math/base/special/pow' );
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var pkg = require( './../package.json' ).name;
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var stdevpn = require( './../lib' );
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// VARIABLES //
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var options = {
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'dtype': 'generic'
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};
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// FUNCTIONS //
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/**
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* Creates a benchmark function.
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*
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* @private
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* @param {PositiveInteger} len - array length
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* @returns {Function} benchmark function
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*/
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function createBenchmark( len ) {
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var x = uniform( len, -10, 10, options );
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return benchmark;
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function benchmark( b ) {
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var v;
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var i;
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b.tic();
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for ( i = 0; i < b.iterations; i++ ) {
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v = stdevpn( x, 1.0 );
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if ( isnan( v ) ) {
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b.fail( 'should not return NaN' );
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}
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}
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b.toc();
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if ( isnan( v ) ) {
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b.fail( 'should not return NaN' );
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}
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b.pass( 'benchmark finished' );
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b.end();
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}
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}
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// MAIN //
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/**
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* Main execution sequence.
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*
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* @private
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*/
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function main() {
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var len;
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var min;
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var max;
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var f;
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var i;
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min = 1; // 10^min
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max = 6; // 10^max
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for ( i = min; i <= max; i++ ) {
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len = pow( 10, i );
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f = createBenchmark( len );
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bench( pkg+':len='+len, f );
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}
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}
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main();

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

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

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/*
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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// TypeScript Version: 4.1
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/// <reference types="@stdlib/types"/>
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import { NumericArray, Collection, AccessorArrayLike } from '@stdlib/types/array';
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/**
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* Input array.
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*/
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type InputArray = NumericArray | Collection<number> | AccessorArrayLike<number>;
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/**
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* Computes the standard deviation of an array using a two-pass algorithm.
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*
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* @param x - input array
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* @param correction - degrees of freedom adjustment
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* @returns standard deviation
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*
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* @example
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* var x = [ 1.0, -2.0, 2.0 ];
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*
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* var v = stdevpn( x, 1.0 );
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* // returns ~2.0817
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*/
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declare function stdevpn( x: InputArray, correction?: number ): number;
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// EXPORTS //
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export = stdevpn;

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

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/*
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* @license Apache-2.0
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*
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* Copyright (c) 2025 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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import AccessorArray = require( '@stdlib/array/base/accessor' );
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import stdevpn = require( './index' );
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// TESTS //
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// The function returns a number...
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{
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const x = new Float64Array( 10 );
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stdevpn( x ); // $ExpectType number
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stdevpn( new AccessorArray( x ) ); // $ExpectType number
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stdevpn( x, 1.0 ); // $ExpectType number
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stdevpn( new AccessorArray( x ), 1.0 ); // $ExpectType number
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}
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// The compiler throws an error if the function is provided a first argument which is not a numeric array...
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{
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stdevpn( 10 ); // $ExpectError
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stdevpn( '10' ); // $ExpectError
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stdevpn( true ); // $ExpectError
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stdevpn( false ); // $ExpectError
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stdevpn( null ); // $ExpectError
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stdevpn( undefined ); // $ExpectError
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stdevpn( {} ); // $ExpectError
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stdevpn( ( x: number ): number => x ); // $ExpectError
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stdevpn( 10, 1.0 ); // $ExpectError
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stdevpn( '10', 1.0 ); // $ExpectError
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stdevpn( true, 1.0 ); // $ExpectError
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stdevpn( false, 1.0 ); // $ExpectError
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stdevpn( null, 1.0 ); // $ExpectError
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stdevpn( undefined, 1.0 ); // $ExpectError
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stdevpn( {}, 1.0 ); // $ExpectError
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stdevpn( ( x: number ): number => x, 1.0 ); // $ExpectError
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}
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// The compiler throws an error if the function is provided a second argument which is not a number...
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{
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const x = new Float64Array( 10 );
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stdevpn( x, '10' ); // $ExpectError
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stdevpn( x, true ); // $ExpectError
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stdevpn( x, false ); // $ExpectError
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stdevpn( x, null ); // $ExpectError
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stdevpn( x, [] ); // $ExpectError
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stdevpn( x, {} ); // $ExpectError
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stdevpn( x, ( x: number ): number => x ); // $ExpectError
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}
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// The compiler throws an error if the function is provided an unsupported number of arguments...
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{
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const x = new Float64Array( 10 );
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stdevpn(); // $ExpectError
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stdevpn( x, 1.0, {} ); // $ExpectError
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}

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