diff --git a/CHANGELOG.md b/CHANGELOG.md
index bb54ded4..296772ab 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -324,6 +324,40 @@ A total of 3 issues were closed in this release:
+
+
+#### [@stdlib/array/base/mskunary4d](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/mskunary4d)
+
+
+
+
+
+##### Features
+
+- [`28db4f2`](https://github.com/stdlib-js/stdlib/commit/28db4f2869749f6a6d6f7ae6476bd27f65052e96) - add `array/base/mskunary4d` [(#3208)](https://github.com/stdlib-js/stdlib/pull/3208)
+
+
+
+
+
+
+
+##### Closed Issues
+
+This release closes the following issue:
+
+[#3176](https://github.com/stdlib-js/stdlib/issues/3176)
+
+
+
+
+
+
+
+
+
+
+
#### [@stdlib/array/base/mskunary5d](https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/array/base/mskunary5d)
@@ -480,9 +514,9 @@ A total of 2 issues were closed in this release:
### Closed Issues
-A total of 7 issues were closed in this release:
+A total of 8 issues were closed in this release:
-[#3135](https://github.com/stdlib-js/stdlib/issues/3135), [#3138](https://github.com/stdlib-js/stdlib/issues/3138), [#3164](https://github.com/stdlib-js/stdlib/issues/3164), [#3177](https://github.com/stdlib-js/stdlib/issues/3177), [#3178](https://github.com/stdlib-js/stdlib/issues/3178), [#3179](https://github.com/stdlib-js/stdlib/issues/3179), [#3180](https://github.com/stdlib-js/stdlib/issues/3180)
+[#3135](https://github.com/stdlib-js/stdlib/issues/3135), [#3138](https://github.com/stdlib-js/stdlib/issues/3138), [#3164](https://github.com/stdlib-js/stdlib/issues/3164), [#3176](https://github.com/stdlib-js/stdlib/issues/3176), [#3177](https://github.com/stdlib-js/stdlib/issues/3177), [#3178](https://github.com/stdlib-js/stdlib/issues/3178), [#3179](https://github.com/stdlib-js/stdlib/issues/3179), [#3180](https://github.com/stdlib-js/stdlib/issues/3180)
@@ -511,6 +545,7 @@ A total of 6 people contributed to this release. Thank you to the following cont
+- [`28db4f2`](https://github.com/stdlib-js/stdlib/commit/28db4f2869749f6a6d6f7ae6476bd27f65052e96) - **feat:** add `array/base/mskunary4d` [(#3208)](https://github.com/stdlib-js/stdlib/pull/3208) _(by Abhijit, Athan Reines)_
- [`fb3c880`](https://github.com/stdlib-js/stdlib/commit/fb3c880b79a6861fe3da4b14eefadafc90d63eda) - **feat:** add `array/base/braodcasted-ternary3d` [(#3228)](https://github.com/stdlib-js/stdlib/pull/3228) _(by Vinit Pandit, Athan Reines)_
- [`2af4b75`](https://github.com/stdlib-js/stdlib/commit/2af4b757cab1052ee7a788f2154f2c7b8c9aa9bb) - **docs:** add note _(by Athan Reines)_
- [`10641b6`](https://github.com/stdlib-js/stdlib/commit/10641b65eee7299d16d0c0239575eafc6b575557) - **docs:** add note _(by Athan Reines)_
diff --git a/base/mskunary4d/README.md b/base/mskunary4d/README.md
new file mode 100644
index 00000000..5ab9cc0f
--- /dev/null
+++ b/base/mskunary4d/README.md
@@ -0,0 +1,124 @@
+
+
+# mskunary4d
+
+> Apply a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assign results to elements in a four-dimensional nested output array.
+
+
+
+
+
+
+
+## Usage
+
+```javascript
+var mskunary4d = require( '@stdlib/array/base/mskunary4d' );
+```
+
+#### mskunary4d( arrays, shape, fcn )
+
+Applies a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assigns results to elements in a four-dimensional nested output array.
+
+```javascript
+var abs = require( '@stdlib/math/base/special/abs' );
+
+var x = [ [ [ [ -1.0, -2.0 ], [ -3.0, -4.0 ] ] ] ];
+var mask = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+
+var shape = [ 1, 1, 2, 2 ];
+
+// Compute the absolute values in-place:
+mskunary4d( [ x, mask, x ], shape, abs );
+// x => [ [ [ [ 1.0, -2.0 ], [ 3.0, 4.0 ] ] ] ]
+```
+
+The function accepts the following arguments:
+
+- **arrays**: array-like object containing one input nested array, an input nested mask array, and one output nested array.
+- **shape**: array shape.
+- **fcn**: unary function to apply.
+
+
+
+
+
+
+
+## Notes
+
+- The function assumes that the input and output arrays have the same shape.
+- An element in an input array is "masked" if the corresponding element in the mask array is non-zero.
+
+
+
+
+
+
+
+## Examples
+
+
+
+```javascript
+var discreteUniform = require( '@stdlib/random/base/discrete-uniform' ).factory;
+var bernoulli = require( '@stdlib/random/base/bernoulli' ).factory;
+var filled4dBy = require( '@stdlib/array/base/filled4d-by' );
+var zeros4d = require( '@stdlib/array/base/zeros4d' );
+var abs = require( '@stdlib/math/base/special/abs' );
+var mskunary4d = require( '@stdlib/array/base/mskunary4d' );
+
+var shape = [ 2, 3, 3, 3 ];
+
+var x = filled4dBy( shape, discreteUniform( -100, 100 ) );
+console.log( x );
+
+var mask = filled4dBy( shape, bernoulli( 0.5 ) );
+console.log( mask );
+
+var y = zeros4d( shape );
+console.log( y );
+
+mskunary4d( [ x, mask, y ], shape, abs );
+console.log( y );
+```
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
diff --git a/base/mskunary4d/benchmark/benchmark.js b/base/mskunary4d/benchmark/benchmark.js
new file mode 100644
index 00000000..49b03bf5
--- /dev/null
+++ b/base/mskunary4d/benchmark/benchmark.js
@@ -0,0 +1,125 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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/base/uniform' ).factory;
+var bernoulli = require( '@stdlib/random/base/bernoulli' ).factory;
+var isnan = require( '@stdlib/math/base/assert/is-nan' );
+var pow = require( '@stdlib/math/base/special/pow' );
+var floor = require( '@stdlib/math/base/special/floor' );
+var identity = require( '@stdlib/math/base/special/identity' );
+var filled4dBy = require( './../../../base/filled4d-by' );
+var zeros4d = require( './../../../base/zeros4d' );
+var numel = require( '@stdlib/ndarray/base/numel' );
+var pkg = require( './../package.json' ).name;
+var mskunary4d = require( './../lib' );
+
+
+// FUNCTIONS //
+
+/**
+* Creates a benchmark function.
+*
+* @private
+* @param {PositiveIntegerArray} shape - array shape
+* @returns {Function} benchmark function
+*/
+function createBenchmark( shape ) {
+ var arrays;
+ var x;
+ var m;
+ var y;
+
+ x = filled4dBy( shape, uniform( -100.0, 100.0 ) );
+ m = filled4dBy( shape, bernoulli( 0.5 ) );
+ y = zeros4d( shape );
+
+ arrays = [ x, m, y ];
+
+ return benchmark;
+
+ /**
+ * Benchmark function.
+ *
+ * @private
+ * @param {Benchmark} b - benchmark instance
+ */
+ function benchmark( b ) {
+ var i0;
+ var i1;
+ var i2;
+ var i3;
+ var i;
+
+ b.tic();
+ for ( i = 0; i < b.iterations; i++ ) {
+ mskunary4d( arrays, shape, identity );
+ i3 = i % shape[ 0 ];
+ i2 = i % shape[ 1 ];
+ i1 = i % shape[ 2 ];
+ i0 = i % shape[ 3 ];
+ if ( isnan( arrays[ 2 ][ i3 ][ i2 ][ i1 ][ i0 ] ) ) {
+ b.fail( 'should not return NaN' );
+ }
+ }
+ b.toc();
+
+ i3 = i % shape[ 0 ];
+ i2 = i % shape[ 1 ];
+ i1 = i % shape[ 2 ];
+ i0 = i % shape[ 3 ];
+ if ( isnan( arrays[ 2 ][ i3 ][ i2 ][ i1 ][ i0 ] ) ) {
+ b.fail( 'should not return NaN' );
+ }
+ b.pass( 'benchmark finished' );
+ b.end();
+ }
+}
+
+
+// MAIN //
+
+/**
+* Main execution sequence.
+*
+* @private
+*/
+function main() {
+ var min;
+ var max;
+ var sh;
+ var N;
+ var f;
+ var i;
+
+ min = 1; // 10^min
+ max = 6; // 10^max
+
+ for ( i = min; i <= max; i++ ) {
+ N = floor( pow( pow( 10, i ), 1.0/4.0 ) );
+ sh = [ N, N, N, N ];
+ f = createBenchmark( sh );
+ bench( pkg+'::equidimensional:size='+numel( sh ), f );
+ }
+}
+
+main();
diff --git a/base/mskunary4d/docs/repl.txt b/base/mskunary4d/docs/repl.txt
new file mode 100644
index 00000000..6ec4e552
--- /dev/null
+++ b/base/mskunary4d/docs/repl.txt
@@ -0,0 +1,34 @@
+
+{{alias}}( arrays, shape, fcn )
+ Applies a unary callback to elements in a four-dimensional nested input
+ array according to elements in a four-dimensional nested mask array and
+ assigns results to elements in a four-dimensional nested output array.
+
+ An element in an input array is "masked" if the corresponding element in the
+ mask array is non-zero.
+
+ Parameters
+ ----------
+ arrays: ArrayLikeObject
+ Array-like object containing one input nested array, an input nested
+ mask array, and one output nested array.
+
+ shape: Array
+ Array shape.
+
+ fcn: Function
+ Unary callback.
+
+ Examples
+ --------
+ > var x = [ [ [ [ -1.0, -2.0 ], [ -3.0, -4.0 ] ] ] ];
+ > var m = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+ > var y = [ [ [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] ] ];
+ > var shape = [ 1, 1, 2, 2 ];
+ > {{alias}}( [ x, m, y ], shape, {{alias:@stdlib/math/base/special/abs}} );
+ > y
+ [ [ [ [ 1.0, 0.0 ], [ 3.0, 4.0 ] ] ] ]
+
+ See Also
+ --------
+
diff --git a/base/mskunary4d/docs/types/index.d.ts b/base/mskunary4d/docs/types/index.d.ts
new file mode 100644
index 00000000..031306e4
--- /dev/null
+++ b/base/mskunary4d/docs/types/index.d.ts
@@ -0,0 +1,71 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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 { Array4D } from '@stdlib/types/array';
+import { Shape4D } from '@stdlib/types/ndarray';
+
+/**
+* Unary callback.
+*
+* @param value - array element
+* @returns result
+*/
+type Unary = ( value: T ) => U;
+
+/**
+* Applies a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assigns results to elements in a four-dimensional nested output array.
+*
+* ## Notes
+*
+* - The function assumes that the input and output arrays have the same shape.
+* - An element in an input array is "masked" if the corresponding element in the mask array is non-zero.
+*
+* @param arrays - array containing one input nested array, an input nested mask array, and one output nested array
+* @param shape - array shape
+* @param fcn - unary callback
+*
+* @example
+* var ones4d = require( '@stdlib/array/base/ones4d' );
+* var zeros4d = require( '@stdlib/array/base/zeros4d' );
+*
+* function scale( x ) {
+* return x * 10.0;
+* }
+*
+* var shape = [ 1, 1, 2, 2 ];
+*
+* var x = ones4d( shape );
+* var y = zeros4d( shape );
+*
+* var mask = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+*
+* mskunary4d( [ x, mask, y ], shape, scale );
+*
+* console.log( y );
+* // => [ [ [ [ 10.0, 0.0 ], [ 10.0, 10.0 ] ] ] ]
+*/
+declare function mskunary4d( arrays: [ Array4D, Array4D, Array4D ], shape: Shape4D, fcn: Unary ): void;
+
+
+// EXPORTS //
+
+export = mskunary4d;
diff --git a/base/mskunary4d/docs/types/test.ts b/base/mskunary4d/docs/types/test.ts
new file mode 100644
index 00000000..5f427ac7
--- /dev/null
+++ b/base/mskunary4d/docs/types/test.ts
@@ -0,0 +1,95 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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 mskunary4d = require( './index' );
+
+/**
+* Unary function.
+*
+* @param value - input value
+* @returns result
+*/
+function fcn( value: number ): number {
+ return value;
+}
+
+
+// TESTS //
+
+// The function returns undefined...
+{
+ const x = [ [ [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] ] ];
+ const m = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+ const y = [ [ [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] ] ];
+
+ mskunary4d( [ x, m, y ], [ 1, 2, 2 ], fcn ); // $ExpectType void
+}
+
+// The compiler throws an error if the function is provided a first argument which is not an array of nested arrays...
+{
+ mskunary4d( 'abc', [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( 3.14, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( true, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( false, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( null, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( [ '1' ], [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( {}, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+ mskunary4d( ( x: number ): number => x, [ 1, 1, 2, 2 ], fcn ); // $ExpectError
+}
+
+// The compiler throws an error if the function is provided a second argument which is not an array of numbers...
+{
+ const x = [ [ [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] ] ];
+ const m = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+ const y = [ [ [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] ] ];
+
+ mskunary4d( [ x, m, y ], 'abc', fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], 3.14, fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], true, fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], false, fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], null, fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ '1' ], fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], {}, fcn ); // $ExpectError
+ mskunary4d( [ x, m, y ], ( x: number ): number => x, fcn ); // $ExpectError
+}
+
+// The compiler throws an error if the function is provided a third argument which is not a valid callback...
+{
+ const x = [ [ [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] ] ];
+ const m = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+ const y = [ [ [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] ] ];
+
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], 'abc' ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], 3.14 ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], true ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], false ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], null ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], [ '1' ] ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], {} ); // $ExpectError
+}
+
+// The compiler throws an error if the function is provided an unsupported number of arguments...
+{
+ const x = [ [ [ [ 1.0, 2.0 ], [ 3.0, 4.0 ] ] ] ];
+ const m = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+ const y = [ [ [ [ 0.0, 0.0 ], [ 0.0, 0.0 ] ] ] ];
+
+ mskunary4d(); // $ExpectError
+ mskunary4d( [ x, m, y ] ); // $ExpectError
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 2 ], fcn, {} ); // $ExpectError
+}
diff --git a/base/mskunary4d/examples/index.js b/base/mskunary4d/examples/index.js
new file mode 100644
index 00000000..3eefefaa
--- /dev/null
+++ b/base/mskunary4d/examples/index.js
@@ -0,0 +1,40 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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/base/discrete-uniform' ).factory;
+var bernoulli = require( '@stdlib/random/base/bernoulli' ).factory;
+var filled4dBy = require( './../../../base/filled4d-by' );
+var zeros4d = require( './../../../base/zeros4d' );
+var abs = require( '@stdlib/math/base/special/abs' );
+var mskunary4d = require( './../lib' );
+
+var shape = [ 2, 3, 3, 3 ];
+
+var x = filled4dBy( shape, discreteUniform( -100, 100 ) );
+console.log( x );
+
+var mask = filled4dBy( shape, bernoulli( 0.5 ) );
+console.log( mask );
+
+var y = zeros4d( shape );
+console.log( y );
+
+mskunary4d( [ x, mask, y ], shape, abs );
+console.log( y );
diff --git a/base/mskunary4d/lib/index.js b/base/mskunary4d/lib/index.js
new file mode 100644
index 00000000..19e50b60
--- /dev/null
+++ b/base/mskunary4d/lib/index.js
@@ -0,0 +1,55 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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';
+
+/**
+* Apply a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assign results to elements in a four-dimensional nested output array.
+*
+* @module @stdlib/array/base/mskunary4d
+*
+* @example
+* var ones4d = require( '@stdlib/array/base/ones4d' );
+* var zeros4d = require( '@stdlib/array/base/zeros4d' );
+* var mskunary4d = require( '@stdlib/array/base/mskunary4d' );
+*
+* function scale( x ) {
+* return x * 10.0;
+* }
+*
+* var shape = [ 1, 1, 2, 2 ];
+*
+* var x = ones4d( shape );
+* var y = zeros4d( shape );
+*
+* var mask = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+*
+* mskunary4d( [ x, mask, y ], shape, scale );
+*
+* console.log( y );
+* // => [ [ [ [ 10.0, 0.0 ], [ 10.0, 10.0 ] ] ] ]
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;
diff --git a/base/mskunary4d/lib/main.js b/base/mskunary4d/lib/main.js
new file mode 100644
index 00000000..057b1fc9
--- /dev/null
+++ b/base/mskunary4d/lib/main.js
@@ -0,0 +1,112 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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';
+
+// MAIN //
+
+/**
+* Applies a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assigns results to elements in a four-dimensional nested output array.
+*
+* ## Notes
+*
+* - The function assumes that the input and output arrays have the same shape.
+*
+* @param {ArrayLikeObject>} arrays - array-like object containing one input nested array, an input nested mask array, and one output nested array
+* @param {NonNegativeIntegerArray} shape - array shape
+* @param {Callback} fcn - unary callback
+* @returns {void}
+*
+* @example
+* var ones4d = require( '@stdlib/array/base/ones4d' );
+* var zeros4d = require( '@stdlib/array/base/zeros4d' );
+*
+* function scale( x ) {
+* return x * 10.0;
+* }
+*
+* var shape = [ 1, 1, 2, 2 ];
+*
+* var x = ones4d( shape );
+* var y = zeros4d( shape );
+*
+* var mask = [ [ [ [ 0, 1 ], [ 0, 0 ] ] ] ];
+*
+* mskunary4d( [ x, mask, y ], shape, scale );
+*
+* console.log( y );
+* // => [ [ [ [ 10.0, 0.0 ], [ 10.0, 10.0 ] ] ] ]
+*/
+function mskunary4d( arrays, shape, fcn ) {
+ var S0;
+ var S1;
+ var S2;
+ var S3;
+ var i0;
+ var i1;
+ var i2;
+ var i3;
+ var x0;
+ var x1;
+ var x2;
+ var y0;
+ var y1;
+ var y2;
+ var m0;
+ var m1;
+ var m2;
+ var x;
+ var y;
+ var m;
+
+ S0 = shape[ 3 ];
+ S1 = shape[ 2 ];
+ S2 = shape[ 1 ];
+ S3 = shape[ 0 ];
+ if ( S0 <= 0 || S1 <= 0 || S2 <= 0 || S3 <= 0 ) {
+ return;
+ }
+ x = arrays[ 0 ];
+ y = arrays[ 2 ];
+ m = arrays[ 1 ];
+ for ( i3 = 0; i3 < S3; i3++ ) {
+ x2 = x[ i3 ];
+ y2 = y[ i3 ];
+ m2 = m[ i3 ];
+ for ( i2 = 0; i2 < S2; i2++ ) {
+ x1 = x2[ i2 ];
+ y1 = y2[ i2 ];
+ m1 = m2[ i2 ];
+ for ( i1 = 0; i1 < S1; i1++ ) {
+ x0 = x1[ i1 ];
+ y0 = y1[ i1 ];
+ m0 = m1[ i1 ];
+ for ( i0 = 0; i0 < S0; i0++ ) {
+ if ( m0[ i0 ] === 0 ) {
+ y0[ i0 ] = fcn( x0[ i0 ] );
+ }
+ }
+ }
+ }
+ }
+}
+
+
+// EXPORTS //
+
+module.exports = mskunary4d;
diff --git a/base/mskunary4d/package.json b/base/mskunary4d/package.json
new file mode 100644
index 00000000..b7b671b3
--- /dev/null
+++ b/base/mskunary4d/package.json
@@ -0,0 +1,73 @@
+{
+ "name": "@stdlib/array/base/mskunary4d",
+ "version": "0.0.0",
+ "description": "Apply a unary callback to elements in a four-dimensional nested input array according to elements in a four-dimensional nested mask array and assign results to elements in a four-dimensional nested output 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",
+ "base",
+ "array",
+ "multidimensional",
+ "ndarray",
+ "matrix",
+ "4d",
+ "unary",
+ "apply",
+ "foreach",
+ "map",
+ "transform",
+ "masked",
+ "mask",
+ "skip",
+ "skipped",
+ "missing",
+ "missing values",
+ "na"
+ ],
+ "__stdlib__": {}
+}
diff --git a/base/mskunary4d/test/test.js b/base/mskunary4d/test/test.js
new file mode 100644
index 00000000..e85e9636
--- /dev/null
+++ b/base/mskunary4d/test/test.js
@@ -0,0 +1,277 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2024 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 zeros4d = require( './../../../base/zeros4d' );
+var mskunary4d = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+ t.ok( true, __filename );
+ t.strictEqual( typeof mskunary4d, 'function', 'main export is a function' );
+ t.end();
+});
+
+tape( 'the function applies a provided callback to a nested input array and assigns results to a nested output array', function test( t ) {
+ var expected;
+ var shape;
+ var x;
+ var y;
+ var m;
+
+ shape = [ 2, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ],
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ],
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ]
+ ];
+
+ expected = [
+ [
+ [
+ [ 1.0, 0.0 ],
+ [ 3.0, 4.0 ]
+ ]
+ ],
+ [
+ [
+ [ 1.0, 0.0 ],
+ [ 3.0, 4.0 ]
+ ]
+ ]
+ ];
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], shape, abs );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+
+ shape = [ 1, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 1, 0 ],
+ [ 1, 0 ]
+ ]
+ ]
+ ];
+
+ expected = [
+ [
+ [
+ [ 0.0, 2.0 ],
+ [ 0.0, 4.0 ]
+ ]
+ ]
+ ];
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], shape, abs );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+ t.end();
+});
+
+tape( 'the function does not invoke a provided callback if provided a shape having a first element equal to zero', function test( t ) {
+ var expected;
+ var shape;
+ var x;
+ var y;
+ var m;
+
+ shape = [ 1, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ]
+ ];
+
+ expected = zeros4d( shape );
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], [ 0, 1, 2, 2 ], clbk );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+ t.end();
+
+ function clbk() {
+ t.ok( false, 'should not invoke callback' );
+ }
+});
+
+tape( 'the function does not invoke a provided callback if provided a shape having a second element equal to zero', function test( t ) {
+ var expected;
+ var shape;
+ var x;
+ var y;
+ var m;
+
+ shape = [ 1, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ]
+ ];
+
+ expected = zeros4d( shape );
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], [ 1, 0, 2, 2 ], clbk );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+ t.end();
+
+ function clbk() {
+ t.ok( false, 'should not invoke callback' );
+ }
+});
+
+tape( 'the function does not invoke a provided callback if provided a shape having a third element equal to zero', function test( t ) {
+ var expected;
+ var shape;
+ var x;
+ var y;
+ var m;
+
+ shape = [ 1, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ]
+ ];
+
+ expected = zeros4d( shape );
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], [ 1, 1, 0, 2 ], clbk );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+ t.end();
+
+ function clbk() {
+ t.ok( false, 'should not invoke callback' );
+ }
+});
+tape( 'the function does not invoke a provided callback if provided a shape having a fourth element equal to zero', function test( t ) {
+ var expected;
+ var shape;
+ var x;
+ var y;
+ var m;
+
+ shape = [ 1, 1, 2, 2 ];
+ x = [
+ [
+ [
+ [ -1.0, -2.0 ],
+ [ -3.0, -4.0 ]
+ ]
+ ]
+ ];
+ m = [
+ [
+ [
+ [ 0, 1 ],
+ [ 0, 0 ]
+ ]
+ ]
+ ];
+
+ expected = zeros4d( shape );
+
+ y = zeros4d( shape );
+ mskunary4d( [ x, m, y ], [ 1, 1, 2, 0 ], clbk );
+
+ t.deepEqual( y, expected, 'returns expected value' );
+ t.end();
+
+ function clbk() {
+ t.ok( false, 'should not invoke callback' );
+ }
+});