diff --git a/lib/node_modules/@stdlib/stats/array/stdev/README.md b/lib/node_modules/@stdlib/stats/array/stdev/README.md new file mode 100644 index 000000000000..0206a6615595 --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/README.md @@ -0,0 +1,121 @@ + + +# stdev + +> Calculate the [standard deviation][standard-deviation] of an array. + +
+ +
+ + + +
+ +## 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 +``` + +
+ + + +
+ +## 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]). + +
+ + + +
+ +## Examples + + + +```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 ); +``` + +
+ + + + + + + + + + + + + + diff --git a/lib/node_modules/@stdlib/stats/array/stdev/benchmark/benchmark.js b/lib/node_modules/@stdlib/stats/array/stdev/benchmark/benchmark.js new file mode 100644 index 000000000000..07cce86cb17b --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/benchmark/benchmark.js @@ -0,0 +1,96 @@ +/** +* @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(); diff --git a/lib/node_modules/@stdlib/stats/array/stdev/docs/repl.txt b/lib/node_modules/@stdlib/stats/array/stdev/docs/repl.txt new file mode 100644 index 000000000000..d5bda912e88d --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/docs/repl.txt @@ -0,0 +1,38 @@ + +{{alias}}( x[, correction] ) + Computes the standard deviation of an array. + + If provided an empty array, the function returns `NaN`. + + Parameters + ---------- + x: Array|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 + -------- + diff --git a/lib/node_modules/@stdlib/stats/array/stdev/docs/types/index.d.ts b/lib/node_modules/@stdlib/stats/array/stdev/docs/types/index.d.ts new file mode 100644 index 000000000000..469f13cca576 --- /dev/null +++ b/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 + +/// + +import { NumericArray, Collection, AccessorArrayLike } from '@stdlib/types/array'; + +/** +* Input array. +*/ +type InputArray = NumericArray | Collection | AccessorArrayLike; + +/** +* 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; diff --git a/lib/node_modules/@stdlib/stats/array/stdev/docs/types/test.ts b/lib/node_modules/@stdlib/stats/array/stdev/docs/types/test.ts new file mode 100644 index 000000000000..1ea6c22c2ca3 --- /dev/null +++ b/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 +} diff --git a/lib/node_modules/@stdlib/stats/array/stdev/examples/index.js b/lib/node_modules/@stdlib/stats/array/stdev/examples/index.js new file mode 100644 index 000000000000..9b0063f92404 --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/examples/index.js @@ -0,0 +1,30 @@ +/** +* @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'; + +var discreteUniform = require( '@stdlib/random/array/discrete-uniform' ); +var stdev = require( './../lib' ); + +var x = discreteUniform( 10, -50, 50, { + 'dtype': 'float64' +}); +console.log( x ); + +var v = stdev( x ); +console.log( v ); diff --git a/lib/node_modules/@stdlib/stats/array/stdev/lib/index.js b/lib/node_modules/@stdlib/stats/array/stdev/lib/index.js new file mode 100644 index 000000000000..c0474f555f00 --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/lib/index.js @@ -0,0 +1,42 @@ +/** +* @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'; + +/** +* Compute the standard deviation of an array. +* +* @module @stdlib/stats/array/stdev +* +* @example +* var stdev = require( '@stdlib/stats/array/stdev' ); +* +* var x = [ 1.0, -2.0, 2.0 ]; +* +* var v = stdev( x, 1.0 ); +* // returns ~2.0817 +*/ + +// MODULES // + +var main = require( './main.js' ); + + +// EXPORTS // + +module.exports = main; diff --git a/lib/node_modules/@stdlib/stats/array/stdev/lib/main.js b/lib/node_modules/@stdlib/stats/array/stdev/lib/main.js new file mode 100644 index 000000000000..f4740d4812d6 --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/lib/main.js @@ -0,0 +1,81 @@ +/** +* @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 isCollection = require( '@stdlib/assert/is-collection' ); +var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive; +var dtypes = require( '@stdlib/array/dtypes' ); +var dtype = require( '@stdlib/array/dtype' ); +var contains = require( '@stdlib/array/base/assert/contains' ); +var join = require( '@stdlib/array/base/join' ); +var strided = require( '@stdlib/stats/base/stdev' ).ndarray; +var format = require( '@stdlib/string/format' ); + + +// VARIABLES // + +var IDTYPES = dtypes( 'real_and_generic' ); +var GENERIC_DTYPE = 'generic'; + + +// MAIN // + +/** +* Computes the standard deviation of an array. +* +* @param {NumericArray} x - input array +* @param {number} correction - degrees of freedom adjustment +* @throws {TypeError} first argument must have a supported data type +* @throws {TypeError} first argument must be an array-like object +* @throws {TypeError} second argument must be an number +* @returns {number} standard deviation +* +* @example +* var x = [ 1.0, -2.0, 2.0 ]; +* +* var v = stdev( x, 1.0 ); +* // returns ~2.0817 +*/ +function stdev( x ) { + var correction; + var dt; + if ( !isCollection( x ) ) { + throw new TypeError( format( 'invalid argument. First argument must be an array-like object. Value: `%s`.', x ) ); + } + dt = dtype( x ) || GENERIC_DTYPE; + if ( !contains( IDTYPES, dt ) ) { + throw new TypeError( format( 'invalid argument. First argument must have one of the following data types: "%s". Data type: `%s`.', join( IDTYPES, '", "' ), dt ) ); + } + if ( arguments.length > 1 ) { + correction = arguments[ 1 ]; + if ( !isNumber( correction ) ) { + throw new TypeError( format( 'invalid argument. Second argument must be a number. Value: `%s`.', correction ) ); + } + } else { + correction = 1.0; + } + return strided( x.length, correction, x, 1, 0 ); +} + + +// EXPORTS // + +module.exports = stdev; diff --git a/lib/node_modules/@stdlib/stats/array/stdev/package.json b/lib/node_modules/@stdlib/stats/array/stdev/package.json new file mode 100644 index 000000000000..a57af736463b --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/package.json @@ -0,0 +1,71 @@ +{ + "name": "@stdlib/stats/array/stdev", + "version": "0.0.0", + "description": "Calculate the standard deviation of an array.", + "license": "Apache-2.0", + "author": { + "name": "The Stdlib Authors", + "url": "https://github.com/stdlib-js/stdlib/graphs/contributors" + }, + "contributors": [ + { + "name": "The Stdlib Authors", + "url": "https://github.com/stdlib-js/stdlib/graphs/contributors" + } + ], + "main": "./lib", + "directories": { + "benchmark": "./benchmark", + "doc": "./docs", + "example": "./examples", + "lib": "./lib", + "test": "./test" + }, + "types": "./docs/types", + "scripts": {}, + "homepage": "https://github.com/stdlib-js/stdlib", + "repository": { + "type": "git", + "url": "git://github.com/stdlib-js/stdlib.git" + }, + "bugs": { + "url": "https://github.com/stdlib-js/stdlib/issues" + }, + "dependencies": {}, + "devDependencies": {}, + "engines": { + "node": ">=0.10.0", + "npm": ">2.7.0" + }, + "os": [ + "aix", + "darwin", + "freebsd", + "linux", + "macos", + "openbsd", + "sunos", + "win32", + "windows" + ], + "keywords": [ + "stdlib", + "stdmath", + "statistics", + "stats", + "mathematics", + "math", + "standard deviation", + "variance", + "var", + "deviation", + "dispersion", + "spread", + "sample standard deviation", + "unbiased", + "stdev", + "std", + "array" + ], + "__stdlib__": {} +} diff --git a/lib/node_modules/@stdlib/stats/array/stdev/test/test.js b/lib/node_modules/@stdlib/stats/array/stdev/test/test.js new file mode 100644 index 000000000000..ced3c57844ab --- /dev/null +++ b/lib/node_modules/@stdlib/stats/array/stdev/test/test.js @@ -0,0 +1,350 @@ +/** +* @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 tape = require( 'tape' ); +var sqrt = require( '@stdlib/math/base/special/sqrt' ); +var isnan = require( '@stdlib/math/base/assert/is-nan' ); +var toAccessorArray = require( '@stdlib/array/base/to-accessor-array' ); +var BooleanArray = require( '@stdlib/array/bool' ); +var Complex128Array = require( '@stdlib/array/complex128' ); +var stdev = require( './../lib' ); + + +// TESTS // + +tape( 'main export is a function', function test( t ) { + t.ok( true, __filename ); + t.strictEqual( typeof stdev, 'function', 'main export is a function' ); + t.end(); +}); + +tape( 'the function has an arity of 1', function test( t ) { + t.strictEqual( stdev.length, 1, 'returns expected value' ); + t.end(); +}); + +tape( 'the function throws an error if provided a first argument which is not an array-like object', function test( t ) { + var values; + var i; + + values = [ + '5', + 5, + NaN, + true, + false, + null, + void 0, + {}, + function noop() {} + ]; + for ( i = 0; i < values.length; i++ ) { + t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] ); + } + t.end(); + + function badValue( value ) { + return function badValue() { + stdev( value ); + }; + } +}); + +tape( 'the function throws an error if provided a first argument which is not an array-like object (correction)', function test( t ) { + var values; + var i; + + values = [ + '5', + 5, + NaN, + true, + false, + null, + void 0, + {}, + function noop() {} + ]; + for ( i = 0; i < values.length; i++ ) { + t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] ); + } + t.end(); + + function badValue( value ) { + return function badValue() { + stdev( value, 1.0 ); + }; + } +}); + +tape( 'the function throws an error if provided a first argument which has an unsupported data type', function test( t ) { + var values; + var i; + + values = [ + new BooleanArray( 4 ), + new Complex128Array( 4 ) + ]; + for ( i = 0; i < values.length; i++ ) { + t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] ); + } + t.end(); + + function badValue( value ) { + return function badValue() { + stdev( value ); + }; + } +}); + +tape( 'the function throws an error if provided a first argument which has an unsupported data type (correction)', function test( t ) { + var values; + var i; + + values = [ + new BooleanArray( 4 ), + new Complex128Array( 4 ) + ]; + for ( i = 0; i < values.length; i++ ) { + t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] ); + } + t.end(); + + function badValue( value ) { + return function badValue() { + stdev( value, 1.0 ); + }; + } +}); + +tape( 'the function throws an error if provided a second argument which is not a number', function test( t ) { + var values; + var i; + + values = [ + '5', + true, + false, + null, + void 0, + [], + {}, + function noop() {} + ]; + for ( i = 0; i < values.length; i++ ) { + t.throws( badValue( values[ i ] ), TypeError, 'throws an error when provided ' + values[ i ] ); + } + t.end(); + + function badValue( value ) { + return function badValue() { + stdev( [ 1, 2, 3 ], value ); + }; + } +}); + +tape( 'the function calculates the population standard deviation of an array', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( x, 0.0 ); + t.strictEqual( v, sqrt( 53.5/x.length ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( x, 0.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, 4.0 ]; + v = stdev( x, 0.0 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the population standard deviation of an array (accessors)', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( toAccessorArray( x ), 0.0 ); + t.strictEqual( v, sqrt( 53.5/x.length ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( toAccessorArray( x ), 0.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, 4.0 ]; + v = stdev( toAccessorArray( x ), 0.0 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the population standard deviation of an array (array-like object)', function test( t ) { + var x; + var v; + + x = { + 'length': 6, + '0': 1.0, + '1': -2.0, + '2': -4.0, + '3': 5.0, + '4': 0.0, + '5': 3.0 + }; + v = stdev( x, 0.0 ); + t.strictEqual( v, sqrt( 53.5/x.length ), 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the sample standard deviation of an array (default)', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( x ); + t.strictEqual( v, sqrt( 53.5/(x.length-1) ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( x ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, 4.0 ]; + v = stdev( x ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the sample standard deviation of an array (default, accessors)', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( toAccessorArray( x ) ); + t.strictEqual( v, sqrt( 53.5/(x.length-1) ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( toAccessorArray( x ) ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, NaN ]; + v = stdev( toAccessorArray( x ) ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the sample standard deviation of an array', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( x, 1.0 ); + t.strictEqual( v, sqrt( 53.5/(x.length-1) ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( x, 1.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, 4.0 ]; + v = stdev( x, 1.0 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'the function calculates the sample standard deviation of an array (accessors)', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 0.0, 3.0 ]; + v = stdev( toAccessorArray( x ), 1.0 ); + t.strictEqual( v, sqrt( 53.5/(x.length-1) ), 'returns expected value' ); + + x = [ -4.0, -4.0 ]; + v = stdev( toAccessorArray( x ), 1.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + + x = [ NaN, NaN ]; + v = stdev( toAccessorArray( x ), 1.0 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'if provided an empty array, the function returns `NaN`', function test( t ) { + var v = stdev( [] ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + t.end(); +}); + +tape( 'if provided an empty array, the function returns `NaN` (accessors)', function test( t ) { + var v = stdev( toAccessorArray( [] ) ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + t.end(); +}); + +tape( 'if provided an array containing a single element, the function returns `0` when computing the population standard deviation', function test( t ) { + var v = stdev( [ 1.0 ], 0.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + t.end(); +}); + +tape( 'if provided an array containing a single element, the function returns `0` when computing the population standard deviation (accessors)', function test( t ) { + var v = stdev( toAccessorArray( [ 1.0 ] ), 0.0 ); + t.strictEqual( v, 0.0, 'returns expected value' ); + t.end(); +}); + +tape( 'if provided a `correction` parameter which is greater than or equal to the input array length, the function returns `NaN`', function test( t ) { + var x; + var v; + + x = [ 1.0, -2.0, -4.0, 5.0, 3.0 ]; + + v = stdev( x, x.length ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + v = stdev( x, x.length+1 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +}); + +tape( 'if provided a `correction` parameter which is greater than or equal to the input array length, the function returns `NaN` (accessors)', function test( t ) { + var x; + var v; + + x = toAccessorArray( [ 1.0, -2.0, -4.0, 5.0, 3.0 ] ); + + v = stdev( x, x.length ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + v = stdev( x, x.length+1 ); + t.strictEqual( isnan( v ), true, 'returns expected value' ); + + t.end(); +});