diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/README.md b/lib/node_modules/@stdlib/stats/incr/nanewstdev/README.md
new file mode 100644
index 000000000000..1727feca5703
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/README.md
@@ -0,0 +1,171 @@
+
+
+# incrnanewstdev
+
+> Compute an [exponentially weighted standard deviation][moving-average] incrementally, ignoring `NaN` values.
+
+
+
+An [exponentially weighted variance][moving-average] can be defined recursively as
+
+
+
+```math
+S_n = \begin{cases} 0 & \textrm{if}\ n = 0 \\ (1 - \alpha) (S_{n-1} + \alpha(x_n - \mu_{n-1})^2) & \textrm{if}\ n > 0 \end{cases}
+```
+
+
+
+
+
+where `μ` is the [exponentially weighted mean][@stdlib/stats/incr/ewmean]. The [exponentially weighted standard deviation][moving-average] is the square root of the [exponentially weighted variance][moving-average].
+
+
+
+
+
+
+
+## Usage
+
+```javascript
+var incrnanewstdev = require( '@stdlib/stats/incr/nanewstdev' );
+```
+
+#### incrnanewstdev( alpha )
+
+Returns an accumulator `function` which incrementally computes an [exponentially weighted standard deviation][moving-average], where `alpha` is a smoothing factor between `0` and `1`, ignoring `NaN` values.
+
+```javascript
+var accumulator = incrnanewstdev( 0.5 );
+```
+
+#### accumulator( \[x] )
+
+If provided an input value `x`, the accumulator function returns an updated standard deviation. If not provided an input value `x`, the accumulator function returns the current standard deviation.
+
+```javascript
+var accumulator = incrnanewstdev( 0.5 );
+
+var s = accumulator();
+// returns null
+
+s = accumulator( 2.0 );
+// returns 0.0
+
+s = accumulator( 1.0 );
+// returns 0.5
+
+s = accumulator( NaN );
+// returns 0.5
+
+s = accumulator( 3.0 );
+// returns ~0.83
+
+s = accumulator();
+// returns ~0.83
+```
+
+
+
+
+
+
+
+## Notes
+
+- Input values are **not** type checked.If non-numeric inputs are possible, but you are advised to type check and handle accordingly **before** passing the value to the accumulator function.
+
+
+
+
+
+
+
+## Examples
+
+
+
+```javascript
+var randu = require( '@stdlib/random/base/randu' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var incrnanewstdev = require( '@stdlib/stats/incr/nanewstdev' );
+
+var accumulator;
+var s;
+var v;
+var i;
+
+// Initialize an accumulator:
+accumulator = incrnanewstdev( 0.5 );
+
+// For each simulated datum, update the exponentially weighted standard deviation...
+for ( i = 0; i < 100; i++ ) {
+ v = (randu() < 0.1) ? NaN : randu() * 100.0;
+ s = accumulator( v );
+}
+console.log( accumulator() );
+```
+
+
+
+
+
+
+
+
+
+* * *
+
+## See Also
+
+- [`@stdlib/stats/incr/ewvariance`][@stdlib/stats/incr/ewvariance]: compute an exponentially weighted variance incrementally.
+- [`@stdlib/stats/incr/mstdev`][@stdlib/stats/incr/mstdev]: compute a moving corrected sample standard deviation incrementally.
+- [`@stdlib/stats/incr/stdev`][@stdlib/stats/incr/stdev]: compute a corrected sample standard deviation incrementally.
+
+
+
+
+
+
+
+
+
+[moving-average]: https://en.wikipedia.org/wiki/Moving_average
+
+[@stdlib/stats/incr/ewmean]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/incr/ewmean
+
+
+
+[@stdlib/stats/incr/ewvariance]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/incr/ewvariance
+
+[@stdlib/stats/incr/mstdev]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/incr/mstdev
+
+[@stdlib/stats/incr/stdev]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/incr/stdev
+
+
+
+
+
+
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/benchmark/benchmark.js b/lib/node_modules/@stdlib/stats/incr/nanewstdev/benchmark/benchmark.js
new file mode 100644
index 000000000000..7a33014e0702
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/benchmark/benchmark.js
@@ -0,0 +1,68 @@
+/**
+* @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 pkg = require( './../package.json' ).name;
+var incrnanewstdev = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+ var f;
+ var i;
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ f = incrnanewstdev( 0.5 );
+ 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 = incrnanewstdev( 0.5 );
+
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ v = acc( i );
+ 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();
+});
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/img/equation_exponentially_weighted_variance.svg b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/img/equation_exponentially_weighted_variance.svg
new file mode 100644
index 000000000000..ec759179e837
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/img/equation_exponentially_weighted_variance.svg
@@ -0,0 +1,89 @@
+
\ No newline at end of file
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/repl.txt b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/repl.txt
new file mode 100644
index 000000000000..963c62d036c8
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/repl.txt
@@ -0,0 +1,37 @@
+
+{{alias}}( α )
+ Returns an accumulator function which incrementally computes an
+ exponentially weighted standard deviation, where α is a smoothing factor
+ between 0 and 1, ignoring `NaN` values.
+
+ If provided a value, the accumulator function returns an updated standard
+ deviation. If not provided a value, the accumulator function returns the
+ current standard deviation.
+
+ Parameters
+ ----------
+ α: number
+ Smoothing factor (value between 0 and 1).
+
+ Returns
+ -------
+ acc: Function
+ Accumulator function.
+
+ Examples
+ --------
+ > var accumulator = {{alias}}( 0.5 );
+ > var s = accumulator()
+ null
+ > s = accumulator( 2.0 )
+ 0.0
+ > s = accumulator( NaN )
+ 0.0
+ > s = accumulator( -5.0 )
+ 3.5
+ > s = accumulator()
+ 3.5
+
+ See Also
+ --------
+
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/index.d.ts b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/index.d.ts
new file mode 100644
index 000000000000..d9aaefb7cffd
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/index.d.ts
@@ -0,0 +1,61 @@
+/*
+* @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
+
+///
+
+/**
+* If provided a value, the accumulator function returns an updated standard deviation. If not provided a value, the accumulator function returns the current standard deviation.
+*
+* @param x - value
+* @returns standard deviation or null
+*/
+type accumulator = ( x?: number ) => number | null;
+
+/**
+* Returns an accumulator function which incrementally computes an exponentially weighted standard deviation, ignoring `NaN` values.
+*
+* @param alpha - smoothing factor
+* @throws must be on the interval `[0,1]`
+* @returns accumulator function
+*
+* @example
+* var accumulator = incrnanewstdev( 0.5 );
+*
+* var s = accumulator();
+* // returns null
+*
+* s = accumulator( 2.0 );
+* // returns 0.0
+*
+* s = accumulator( NaN );
+* // returns 0.0
+*
+* s = accumulator( -5.0 );
+* // returns 3.5
+*
+* s = accumulator();
+* // returns 3.5
+*/
+declare function incrnanewstdev( alpha: number ): accumulator;
+
+
+// EXPORTS //
+
+export = incrnanewstdev;
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/test.ts b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/test.ts
new file mode 100644
index 000000000000..304949f455f7
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/docs/types/test.ts
@@ -0,0 +1,60 @@
+/*
+* @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 incrnanewstdev = require( './index' );
+
+
+// TESTS //
+
+// The function returns an accumulator function...
+{
+ incrnanewstdev( 0.5 ); // $ExpectType accumulator
+}
+
+// The compiler throws an error if the function is provided an argument that is not a number...
+{
+ incrnanewstdev( '5' ); // $ExpectError
+ incrnanewstdev( true ); // $ExpectError
+ incrnanewstdev( false ); // $ExpectError
+ incrnanewstdev( null ); // $ExpectError
+ incrnanewstdev( undefined ); // $ExpectError
+ incrnanewstdev( [] ); // $ExpectError
+ incrnanewstdev( {} ); // $ExpectError
+ incrnanewstdev( ( x: number ): number => x ); // $ExpectError
+}
+
+// The function returns an accumulator function which returns an accumulated result...
+{
+ const acc = incrnanewstdev( 0.5 );
+
+ acc(); // $ExpectType number | null
+ acc( 3.14 ); // $ExpectType number | null
+}
+
+// The compiler throws an error if the returned accumulator function is provided invalid arguments...
+{
+ const acc = incrnanewstdev( 0.5 );
+
+ acc( '5' ); // $ExpectError
+ acc( true ); // $ExpectError
+ acc( false ); // $ExpectError
+ acc( null ); // $ExpectError
+ acc( [] ); // $ExpectError
+ acc( {} ); // $ExpectError
+ acc( ( x: number ): number => x ); // $ExpectError
+}
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/examples/index.js b/lib/node_modules/@stdlib/stats/incr/nanewstdev/examples/index.js
new file mode 100644
index 000000000000..99e8b99aca7f
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/examples/index.js
@@ -0,0 +1,37 @@
+/**
+* @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 randu = require( '@stdlib/random/base/randu' );
+var incrnanewstdev = require( './../lib' );
+
+// Initialize an accumulator:
+var accumulator = incrnanewstdev( 0.5 );
+
+// For each simulated datum, update the exponentially weighted standard deviation...
+console.log( '\nValue\tStDev\n' );
+var s;
+var v;
+var i;
+for ( i = 0; i < 100; i++ ) {
+ v = ( randu() < 0.1 ) ? NaN : randu() * 100.0; // 10% chance of a NaN
+ s = accumulator( v );
+ console.log( '%d\t%d', v.toFixed( 4 ), ( s === null ) ? NaN : s.toFixed( 4 ) );
+}
+console.log( '\nFinal StDev: %d\n', accumulator() );
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/index.js b/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/index.js
new file mode 100644
index 000000000000..e8c0b6b737af
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/index.js
@@ -0,0 +1,54 @@
+/**
+* @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 an exponentially weighted standard deviation incrementally, ignoring `NaN` values.
+*
+* @module @stdlib/stats/incr/nanewstdev
+*
+* @example
+* var increwstdev = require( '@stdlib/stats/incr/nanewstdev' );
+*
+* var accumulator = increwstdev();
+*
+* var s = accumulator();
+* // returns null
+*
+* s = accumulator( 2.0 );
+* // returns 0.0
+*
+* s = accumulator( NaN );
+* // returns 0.0
+*
+* s = accumulator( -5.0 );
+* // returns 3.5
+*
+* s = accumulator();
+* // returns 3.5
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/main.js b/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/main.js
new file mode 100644
index 000000000000..a7de9ec2809a
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/lib/main.js
@@ -0,0 +1,79 @@
+/**
+* @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 isnan = require( '@stdlib/math/base/assert/is-nan' );
+var increwstdev = require( '@stdlib/stats/incr/ewstdev' );
+
+
+// MAIN //
+
+/**
+* Returns an accumulator function which incrementally computes an exponentially weighted standard deviation, ignoring `NaN` values.
+*
+* @param {NonNegativeNumber} alpha - smoothing factor
+* @throws {TypeError} must provide a nonnegative number
+* @throws {RangeError} must be on the interval `[0,1]`
+* @returns {Function} accumulator function
+*
+* @example
+* var accumulator = incrnanewstdev( 0.5 );
+*
+* var s = accumulator();
+* // returns null
+*
+* s = accumulator( 2.0 );
+* // returns 0.0
+*
+* s = accumulator( NaN );
+* // returns 0.0
+*
+* s = accumulator( -5.0 );
+* // returns 3.5
+*
+* s = accumulator();
+* // returns 3.5
+*/
+function incrnanewstdev( alpha ) {
+ var ewstdev;
+
+ ewstdev = increwstdev(alpha);
+ return accumulator;
+
+ /**
+ * If provided a value, the accumulator function returns an updated standard deviation. If not provided a value, the accumulator function returns the current standard deviation.
+ *
+ * @private
+ * @param {number} [x] - new value
+ * @returns {(number|null)} standard deviation or null
+ */
+ function accumulator( x ) {
+ if ( arguments.length === 0 || isnan( x ) ) {
+ return ewstdev();
+ }
+ return ewstdev( x );
+ }
+}
+
+
+// EXPORTS //
+
+module.exports = incrnanewstdev;
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/package.json b/lib/node_modules/@stdlib/stats/incr/nanewstdev/package.json
new file mode 100644
index 000000000000..4bfef3d5ca93
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/package.json
@@ -0,0 +1,74 @@
+{
+ "name": "@stdlib/stats/incr/nanewstdev",
+ "version": "0.0.0",
+ "description": "Compute an exponentially weighted standard deviation incrementally, ignoring `NaN` values.",
+ "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",
+ "stdev",
+ "std",
+ "variance",
+ "var",
+ "standard",
+ "deviation",
+ "dispersion",
+ "weighted",
+ "exponential",
+ "emsd",
+ "emv",
+ "ewmv",
+ "ewmsd",
+ "incremental",
+ "accumulator"
+ ]
+}
diff --git a/lib/node_modules/@stdlib/stats/incr/nanewstdev/test/test.js b/lib/node_modules/@stdlib/stats/incr/nanewstdev/test/test.js
new file mode 100644
index 000000000000..1aed109b702a
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nanewstdev/test/test.js
@@ -0,0 +1,158 @@
+/**
+* @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 pow = require( '@stdlib/math/base/special/pow' );
+var sqrt = require( '@stdlib/math/base/special/sqrt' );
+var incrnanewstdev = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+ t.ok( true, __filename );
+ t.strictEqual( typeof incrnanewstdev, 'function', 'main export is a function' );
+ t.end();
+});
+
+tape( 'the function throws an error if not provided a nonnegative number', function test( t ) {
+ var values;
+ var i;
+
+ values = [
+ '5',
+ -5.0,
+ 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() {
+ incrnanewstdev( value );
+ };
+ }
+});
+
+tape( 'the function throws an error if provided a nonnegative number which does not reside on the interval `[0,1]`', function test( t ) {
+ var values;
+ var i;
+
+ values = [
+ 1.5,
+ 3.14,
+ 1.0001,
+ 1.0e300
+ ];
+
+ for ( i = 0; i < values.length; i++ ) {
+ t.throws( badValue( values[i] ), RangeError, 'throws an error when provided '+values[i] );
+ }
+ t.end();
+
+ function badValue( value ) {
+ return function badValue() {
+ incrnanewstdev( value );
+ };
+ }
+});
+
+tape( 'the function returns an accumulator function', function test( t ) {
+ t.equal( typeof incrnanewstdev( 0.5 ), 'function', 'returns a function' );
+ t.end();
+});
+
+tape( 'the initial accumulated value is `null`', function test( t ) {
+ var acc = incrnanewstdev( 0.5 );
+ t.equal( acc(), null, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the accumulator function incrementally computes an exponentially weighted standard deviation', function test( t ) {
+ var expected;
+ var actual;
+ var data;
+ var acc;
+ var N;
+ var i;
+
+ data = [
+ 2.0,
+ NaN,
+ 3.0,
+ 2.0,
+ 4.0,
+ NaN,
+ 3.0,
+ 4.0
+ ];
+ N = data.length;
+
+ // Note: manually computed using the recurrence relation S_n = (1-α)(S_{n-1} + α(x_n - mu_{n-1})^2) = S_n = (1-α)S_{n-1} + α(1-α)(x_n - mu_{n-1})^2
+ expected = [
+ 0.0, // m = 2.0, s2 = 0.0
+ 0.0, // Ignore NaN values
+ sqrt( (0.5*0.0) + (0.25*pow( 3.0-2.0, 2 )) ), // m = 2.5, s2 = 0.25
+ sqrt( (0.5*0.25) + (0.25*pow( 2.0-2.5, 2 )) ), // m = 2.25, s2 = 0.1875
+ sqrt( (0.5*0.1875) + (0.25*pow( 4.0-2.25, 2 )) ), // m = 3.125, s2 = 0.859375
+ sqrt( (0.5*0.1875) + (0.25*pow( 4.0-2.25, 2 )) ), // Ignore NaN values
+ sqrt( (0.5*0.859375) + (0.25*pow( 3.0-3.125, 2 )) ), // m = 3.0625, s2 = 0.43359375
+ sqrt( (0.5*0.43359375) + (0.25*pow( 4.0-3.0625, 2 )) ) // m = 3.53125, s2 = 0.4365234375
+ ];
+ actual = [];
+
+ acc = incrnanewstdev( 0.5 );
+
+ for ( i = 0; i < N; i++ ) {
+ actual.push( acc( data[ i ] ) );
+ }
+ t.deepEqual( actual, expected, 'returns expected values' );
+ t.end();
+});
+
+tape( 'if not provided an input value, the accumulator function returns the current standard deviation', function test( t ) {
+ var data;
+ var acc;
+ var i;
+
+ data = [
+ 2.0, // m = 2.0, s2 = 0.0
+ 3.0, // m = 2.5, s2 = 0.25
+ NaN, // Ignore NaN values
+ 1.0 // m = 1.75, s2 = 0.6875
+ ];
+ acc = incrnanewstdev( 0.5 );
+ for ( i = 0; i < data.length; i++ ) {
+ acc( data[ i ] );
+ }
+ t.equal( acc(), sqrt( 0.6875 ), 'returns expected value' );
+ t.end();
+});