diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/README.md b/lib/node_modules/@stdlib/stats/incr/nancovariance/README.md
new file mode 100644
index 000000000000..b50811877bdf
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/README.md
@@ -0,0 +1,121 @@
+
+
+# incrnancovariance
+
+> Compute an incremental sample covariance while ignoring `NaN` values.
+
+
+
+## Usage
+
+```javascript
+var nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+```
+
+#### incrnancovariance
+
+Returns an accumulator function which incrementally computes a sample covariance, ignoring any input pairs that contain NaN values. The accumulator returns null until at least two valid data pairs have been provided.
+
+```javascript
+var accumulator = nancovariance();
+```
+
+#### accumulator(`[x, y]`)
+
+If provided a pair of numeric input values `[x, y]`, the accumulator updates and returns the sample covariance. If not provided any input values, the accumulator returns the current sample covariance.
+
+```javascript
+var accumulator = nancovariance();
+
+var cov = accumulator();
+// returns null
+
+cov = accumulator( 2.0, 1.0 );
+// returns null
+
+cov = accumulator( NaN, 1.0 );
+// returns null
+
+cov = accumulator( 4.0, 5.0 );
+// returns 4.0
+
+cov = accumulator();
+// returns 4.0
+```
+
+
+
+
+
+
+
+## Examples
+
+
+
+```javascript
+var randu = require( '@stdlib/random/base/randu' );
+var nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+
+var accumulator;
+var i;
+var x;
+var y;
+accumulator = nancovariance();
+for ( i = 0; i < 100; i++ ) {
+ x = ( randu() < 0.2 ) ? NaN : randu() * 100.0;
+ y = ( randu() < 0.2 ) ? NaN : randu() * 100.0;
+ accumulator( x, y );
+}
+console.log( accumulator() );
+```
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+[@stdlib/stats/incr/nansum]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/stats/incr/nansum
+
+
+
+
+
+
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/benchmark/benchmark.js b/lib/node_modules/@stdlib/stats/incr/nancovariance/benchmark/benchmark.js
new file mode 100644
index 000000000000..7f43432ae8a6
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/benchmark/benchmark.js
@@ -0,0 +1,72 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2020 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 nancovariance = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+ var acc;
+ var i;
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ acc = nancovariance();
+ if ( typeof acc !== 'function' ) {
+ b.fail( 'should return a function' );
+ }
+ }
+ b.toc();
+ if ( typeof acc !== 'function' ) {
+ b.fail( 'should return a function' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+});
+
+bench( pkg+'::accumulator', function benchmark( b ) {
+ var acc;
+ var x;
+ var y;
+ var v;
+ var i;
+
+ acc = nancovariance();
+
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ x = ( randu() < 0.1 ) ? NaN : randu()*10; // ~10% NaN
+ y = ( randu() < 0.1 ) ? NaN : randu()*10; // ~10% NaN
+ v = acc( x, y );
+ if ( v !== v && i > 1 ) {
+ b.fail( 'accumulator should not return NaN once enough valid data' );
+ }
+ }
+ 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/nancovariance/docs/repl.txt b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/repl.txt
new file mode 100644
index 000000000000..d696647ca7ae
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/repl.txt
@@ -0,0 +1,28 @@
+{{alias}}()
+ Returns an accumulator function which incrementally updates a count,
+ ignoring `NaN` values.
+
+ If provided a value, the accumulator function returns an updated count. If
+ not provided a value, the accumulator function returns the current count.
+
+ Returns
+ -------
+ acc: Function
+ Accumulator function.
+
+ Examples
+ --------
+ > var accumulator = {{alias}}();
+ > var v = accumulator()
+ null
+ > v = accumulator( 2.0 )
+ null
+ > v = accumulator( NaN )
+ null
+ > v = accumulator( -5.0 )
+ NaN
+ > v = accumulator()
+ NaN
+
+ See Also
+ --------
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/index.d.ts b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/index.d.ts
new file mode 100644
index 000000000000..7a8e9967ae69
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/index.d.ts
@@ -0,0 +1,68 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2020 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 pair of values, updates and returns the sample covariance;
+ * otherwise, returns the current sample covariance.
+ *
+ * @param x - first numeric value
+ * @param y - second numeric value
+ * @returns sample covariance or null
+ */
+interface Accumulator {
+ ( x: number, y: number ): number | null;
+ (): number | null;
+}
+
+
+/**
+* Returns an accumulator function which incrementally computes a count, ignoring `NaN` values.
+*
+* @returns accumulator function
+*
+* @example
+* var nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+*
+* var acc = nancovariance();
+*
+* var cov = acc();
+* // returns null
+*
+* cov = acc( 2.0, 1.0 );
+* // returns null
+*
+* cov = acc( NaN, 5.0 );
+* // returns null
+*
+* cov = acc( 4.0, 5.0 );
+* // returns 4.0
+*
+* cov = acc();
+* // returns 4.0
+*/
+
+declare function nancovariance( ...args: [] ): Accumulator;
+
+
+// EXPORTS //
+
+export = nancovariance;
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/test.ts b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/test.ts
new file mode 100644
index 000000000000..0bf914168755
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/docs/types/test.ts
@@ -0,0 +1,50 @@
+/*
+* @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 nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+
+// TESTS //
+
+// The function returns an accumulator function...
+{
+ nancovariance(); // $ExpectType Accumulator
+}
+
+// The compiler throws an error if the function is provided any arguments...
+{
+ nancovariance( 3 ); // $ExpectError
+ nancovariance( 3, 0.0 ); // $ExpectError
+}
+
+// The function returns an accumulator function which returns an accumulated result...
+{
+ const acc = nancovariance();
+ acc(); // $ExpectType number | null
+ acc( 2.0, 1.0 ); // $ExpectType number | null
+}
+
+// The compiler throws an error if the returned accumulator function is provided invalid arguments...
+{
+ const acc = nancovariance();
+ acc( '5', 2.0 ); // $ExpectError
+ acc( true, 2.0 ); // $ExpectError
+ acc( 2.0 ); // $ExpectError
+ acc( null, 2.0 ); // $ExpectError
+ acc( [], {} ); // $ExpectError
+ acc( ( x: number ): number => x ); // $ExpectError
+}
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/examples/index.js b/lib/node_modules/@stdlib/stats/incr/nancovariance/examples/index.js
new file mode 100644
index 000000000000..3307796fcc3d
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/examples/index.js
@@ -0,0 +1,35 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2020 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 nancovariance = require( './../lib' );
+
+var acc = nancovariance();
+
+var dataX = [ 2.0, 2.0, NaN, 3.0, 5.0 ];
+var dataY = [ 1.0, 5.0, 4.0, NaN, 5.0 ];
+
+var i;
+var cov;
+for ( i = 0; i < dataX.length; i++ ) {
+ cov = acc( dataX[ i ], dataY[ i ] );
+ console.log( 'x=%s, y=%s, cov=%s', dataX[ i ], dataY[ i ], ( cov === null ) ? 'null' : cov.toString() );
+}
+
+console.log( '\nFinal sample covariance:', acc() );
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/index.js b/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/index.js
new file mode 100644
index 000000000000..da2a461fcc5e
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/index.js
@@ -0,0 +1,54 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2020 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 incremental sample covariance while ignoring NaN values.
+*
+* @module @stdlib/stats/incr/nancovariance
+*
+* @example
+* var nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+*
+* var acc = nancovariance();
+*
+* var cov = acc();
+* // returns null
+*
+* cov = acc( 2.0, 1.0 );
+* // returns null (covariance is undefined for a single pair)
+*
+* cov = acc( NaN , 5.0 );
+* // returns null (An input with a NaN is ignored)
+*
+* cov = acc( 4.0, 5.0 );
+* // returns 4.0
+*
+* cov = acc();
+* // returns 4.0
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/main.js b/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/main.js
new file mode 100644
index 000000000000..4ea0de981100
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/lib/main.js
@@ -0,0 +1,85 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2020 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 covariance = require( '@stdlib/stats/incr/covariance' );
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+
+
+// MAIN //
+
+/**
+* Returns an accumulator function which incrementally computes a sample covariance.
+*
+* @returns {Function} accumulator function
+*
+* @example
+* var nancovariance = require( '@stdlib/stats/incr/nancovariance' );
+*
+* var acc = nancovariance();
+*
+* var cov = acc();
+* // returns null
+*
+* cov = acc( 2.0, 1.0 );
+* // returns null
+*
+* cov = acc( NaN, 5.0 );
+* // returns null
+*
+* cov = acc( 4.0, 5.0 );
+* // returns 4.0
+*
+* cov = acc();
+* // returns 4.0
+*/
+function nancovariance() {
+ var count = 0;
+ var acc = covariance();
+ return accumulator;
+
+ /**
+ * Updates and returns the sample covariance when provided two numeric arguments.
+ * If no arguments are provided, returns the current sample covariance.
+ *
+ * @private
+ * @param {number} [x] - new x value
+ * @param {number} [y] - new y value
+ * @returns {(number|null)} sample covariance or null
+ */
+ function accumulator( x, y ) {
+ var val;
+ if ( arguments.length === 0 ) {
+ return ( count < 2 ) ? null : acc();
+ }
+ if ( isnan( x ) || isnan( y ) ) {
+ return ( count < 2 ) ? null : acc();
+ }
+ count += 1;
+ val = acc( x, y );
+ return ( count < 2 ) ? null : val;
+ }
+}
+
+
+// EXPORTS //
+
+module.exports = nancovariance;
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/package.json b/lib/node_modules/@stdlib/stats/incr/nancovariance/package.json
new file mode 100644
index 000000000000..b80e2ab2744e
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/package.json
@@ -0,0 +1,60 @@
+{
+ "name": "@stdlib/stats/incr/nancovariance",
+ "version": "0.0.0",
+ "description": "Compute an incremental sample covariance while 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",
+ "statistics",
+ "covariance",
+ "incremental",
+ "accumulator",
+ "nan",
+ "sample covariance"
+ ]
+}
diff --git a/lib/node_modules/@stdlib/stats/incr/nancovariance/test/test.js b/lib/node_modules/@stdlib/stats/incr/nancovariance/test/test.js
new file mode 100644
index 000000000000..43e9fc9afae9
--- /dev/null
+++ b/lib/node_modules/@stdlib/stats/incr/nancovariance/test/test.js
@@ -0,0 +1,127 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2018 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 abs = require( '@stdlib/math/base/special/abs' );
+var EPS = require( '@stdlib/constants/float64/eps' );
+var nancovariance = require( './../lib' );
+
+
+// MAIN //
+
+tape( 'main export is a function', function test( t ) {
+ t.ok( true, __filename );
+ t.strictEqual( typeof nancovariance, 'function', 'main export is a function' );
+ t.end();
+});
+
+// Additional tests...
+
+tape( 'the function returns an accumulator function', function test( t ) {
+ var acc = nancovariance();
+ t.strictEqual( typeof acc, 'function', 'returns a function' );
+ t.end();
+});
+
+tape( 'the accumulator function returns null if no valid pairs have been provided', function test( t ) {
+ var acc = nancovariance();
+ t.equal( acc(), null, 'returns null initially' );
+
+ // Provide an invalid pair:
+ acc( NaN, 5.0 );
+ t.equal( acc(), null, 'still null after invalid pair' );
+ t.end();
+});
+
+tape( 'the accumulator function returns null if only one valid pair has been provided', function test( t ) {
+ var acc = nancovariance();
+
+ // Add the first valid pair:
+ acc( 2.0, 1.0 );
+ t.equal( acc(), null, 'returns null for single valid pair' );
+ t.end();
+});
+
+tape( 'the accumulator function computes sample covariance once two valid pairs have been provided', function test( t ) {
+ var acc = nancovariance();
+ var cov;
+
+ // Pair #1:
+ cov = acc( 2.0, 1.0 );
+ t.equal( cov, null, 'still null with only one valid pair' );
+
+ // Pair #2:
+ cov = acc( 4.0, 5.0 );
+ t.equal( cov, 4.0, 'returns sample covariance after second valid pair' );
+
+ // Current covariance with no arguments:
+ t.equal( acc(), 4.0, 'returns current covariance' );
+ t.end();
+});
+
+tape( 'the accumulator function skips pairs containing NaN', function test( t ) {
+ var acc = nancovariance();
+ var cov;
+
+ // Provide first valid pair:
+ cov = acc( 2.0, 1.0 );
+ t.equal( cov, null, 'null with only one valid pair' );
+
+ // Invalid pair => skip:
+ cov = acc( NaN, 10.0 );
+ t.equal( cov, null, 'still null, as second pair is invalid' );
+
+ // Provide second valid pair:
+ cov = acc( 2.0, 5.0 );
+ // For (2,1) and (2,5): same X => covariance=0
+ t.equal( cov, 0.0, 'returns 0.0 for these pairs' );
+
+ // Provide third valid pair:
+ cov = acc( 5.0, 9.0 );
+ t.equal( typeof cov, 'number', 'returns a number after third valid pair' );
+ t.end();
+});
+
+tape( 'the accumulator function computes correct covariance for multiple valid pairs interspersed with invalid pairs', function test( t ) {
+ var expected = 14.0/3.0;
+ var delta;
+ var data = [
+ [ 2.0, 1.0 ],
+ [ NaN, 4.0 ],
+ [ 4.0, 5.0 ],
+ [ 3.0, 7.0 ],
+ [ NaN, NaN ],
+ [ 5.0, 11.0 ]
+ ];
+ var acc = nancovariance();
+ var cov;
+ var tol;
+ var i;
+ for ( i = 0; i < data.length; i++ ) {
+ cov = acc( data[i][0], data[i][1] );
+ }
+ delta = abs( cov - expected );
+ tol = EPS * abs( expected );
+ t.equal( typeof cov, 'number', 'returns a number' );
+ t.ok( delta < tol, 'within tolerance. Actual: '+cov+'. Expected: '+expected+'. delta: '+delta+'. tol: '+tol+'.' );
+ t.end();
+});