diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/README.md b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/README.md
new file mode 100644
index 000000000000..5cadd58a71f6
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/README.md
@@ -0,0 +1,119 @@
+<!--
+
+@license Apache-2.0
+
+Copyright (c) 2026 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.
+
+-->
+
+# isLegendDirection
+
+> Test if an input value is a supported [legend direction][@stdlib/plot/vega/legend/directions].
+
+<!-- Section to include introductory text. Make sure to keep an empty line after the intro `section` element and another before the `/section` close. -->
+
+<section class="intro">
+
+</section>
+
+<!-- /.intro -->
+
+<!-- Package usage documentation. -->
+
+<section class="usage">
+
+## Usage
+
+```javascript
+var isLegendDirection = require( '@stdlib/plot/vega/base/assert/is-legend-direction' );
+```
+
+#### isLegendDirection( value )
+
+Tests if an input value is a supported [legend direction][@stdlib/plot/vega/legend/directions].
+
+```javascript
+var bool = isLegendDirection( 'horizontal' );
+// returns true
+
+bool = isLegendDirection( 'foo' );
+// returns false
+```
+
+</section>
+
+<!-- /.usage -->
+
+<!-- Package usage notes. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="notes">
+
+</section>
+
+<!-- /.notes -->
+
+<!-- Package usage examples. -->
+
+<section class="examples">
+
+## Examples
+
+<!-- eslint no-undef: "error" -->
+
+```javascript
+var isLegendDirection = require( '@stdlib/plot/vega/base/assert/is-legend-direction' );
+
+var bool = isLegendDirection( 'horizontal' );
+// returns true
+
+bool = isLegendDirection( 'vertical' );
+// returns true
+
+bool = isLegendDirection( '' );
+// returns false
+
+bool = isLegendDirection( 'foo' );
+// returns false
+```
+
+</section>
+
+<!-- /.examples -->
+
+<!-- Section to include cited references. If references are included, add a horizontal rule *before* the section. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="references">
+
+</section>
+
+<!-- /.references -->
+
+<!-- Section for related `stdlib` packages. Do not manually edit this section, as it is automatically populated. -->
+
+<section class="related">
+
+</section>
+
+<!-- /.related -->
+
+<!-- Section for all links. Make sure to keep an empty line after the `section` element and another before the `/section` close. -->
+
+<section class="links">
+
+[@stdlib/plot/vega/legend/directions]: https://github.com/stdlib-js/stdlib/tree/develop/lib/node_modules/%40stdlib/plot/vega/legend/directions
+
+</section>
+
+<!-- /.links -->
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/benchmark/benchmark.js b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/benchmark/benchmark.js
new file mode 100644
index 000000000000..9fb448a016ad
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/benchmark/benchmark.js
@@ -0,0 +1,62 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 isBoolean = require( '@stdlib/assert/is-boolean' ).isPrimitive;
+var pkg = require( './../package.json' ).name;
+var isLegendDirection = require( './../lib' );
+
+
+// MAIN //
+
+bench( pkg, function benchmark( b ) {
+	var values;
+	var out;
+	var v;
+	var i;
+
+	values = [
+		'horizontal',
+		'vertical',
+
+		'foo',
+		'bar',
+		'',
+		'beep',
+		'boop'
+	];
+
+	b.tic();
+	for ( i = 0; i < b.iterations; i++ ) {
+		v = values[ i%values.length ];
+		out = isLegendDirection( v );
+		if ( typeof out !== 'boolean' ) {
+			b.fail( 'should return a boolean' );
+		}
+	}
+	b.toc();
+	if ( !isBoolean( out ) ) {
+		b.fail( 'should return a boolean' );
+	}
+	b.pass( 'benchmark finished' );
+	b.end();
+});
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/repl.txt b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/repl.txt
new file mode 100644
index 000000000000..521e5e79cc0d
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/repl.txt
@@ -0,0 +1,29 @@
+
+{{alias}}( value )
+    Tests if an input value is a supported legend direction.
+
+    Parameters
+    ----------
+    value: any
+        Value to test.
+
+    Returns
+    -------
+    bool: boolean
+        Boolean indicating if an input value is a supported legend
+        direction.
+
+    Examples
+    --------
+    > var bool = {{alias}}( 'horizontal' )
+    true
+    > bool = {{alias}}( 'vertical' )
+    true
+    > bool = {{alias}}( '' )
+    false
+    > bool = {{alias}}( 'beep' )
+    false
+
+    See Also
+    --------
+
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/index.d.ts b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/index.d.ts
new file mode 100644
index 000000000000..8d169402d54b
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/index.d.ts
@@ -0,0 +1,45 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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
+
+/**
+* Tests whether an input value is a supported legend direction.
+*
+* @param v - value to test
+* @returns boolean indicating whether an input value is a supported legend direction
+*
+* @example
+* var bool = isLegendDirection( 'horizontal' );
+* // returns true
+*
+* bool = isLegendDirection( 'vertical' );
+* // returns true
+*
+* bool = isLegendDirection( 'bar' );
+* // returns false
+*
+* bool = isLegendDirection( 'foo' );
+* // returns false
+*/
+declare function isLegendDirection( v: any ): boolean;
+
+
+// EXPORTS //
+
+export = isLegendDirection;
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/test.ts b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/test.ts
new file mode 100644
index 000000000000..08a08f4d6331
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/docs/types/test.ts
@@ -0,0 +1,34 @@
+/*
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 isLegendDirection = require( './index' );
+
+
+// TESTS //
+
+// The function returns a boolean...
+{
+	isLegendDirection( 'horizontal' ); // $ExpectType boolean
+	isLegendDirection( 'foo' ); // $ExpectType boolean
+}
+
+// The compiler throws an error if the function is provided an unsupported number of arguments...
+{
+	isLegendDirection(); // $ExpectError
+	isLegendDirection( undefined, 123 ); // $ExpectError
+}
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/examples/index.js b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/examples/index.js
new file mode 100644
index 000000000000..d312b7d96540
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/examples/index.js
@@ -0,0 +1,37 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 isLegendDirection = require( './../lib' );
+
+var bool = isLegendDirection( 'horizontal' );
+console.log( bool );
+// => true
+
+bool = isLegendDirection( 'vertical' );
+console.log( bool );
+// => true
+
+bool = isLegendDirection( '' );
+console.log( bool );
+// => false
+
+bool = isLegendDirection( 'foo' );
+console.log( bool );
+// => false
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/index.js b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/index.js
new file mode 100644
index 000000000000..58672a81ad4d
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/index.js
@@ -0,0 +1,49 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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';
+
+/**
+* Test whether an input value is a supported legend direction.
+*
+* @module @stdlib/plot/vega/base/assert/is-legend-direction
+*
+* @example
+* var isLegendDirection = require( '@stdlib/plot/vega/base/assert/is-legend-direction' );
+*
+* var bool = isLegendDirection( 'horizontal' );
+* // returns true
+*
+* bool = isLegendDirection( 'vertical' );
+* // returns true
+*
+* bool = isLegendDirection( 'bar' );
+* // returns false
+*
+* bool = isLegendDirection( 'foo' );
+* // returns false
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/main.js b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/main.js
new file mode 100644
index 000000000000..7e5652f45957
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/lib/main.js
@@ -0,0 +1,55 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 contains = require( '@stdlib/array/base/assert/contains' ).factory;
+var values = require( '@stdlib/plot/vega/legend/directions' );
+
+
+// MAIN //
+
+/**
+* Tests whether an input value is a supported legend direction.
+*
+* @name isLegendDirection
+* @type {Function}
+* @param {*} v - value to test
+* @returns {boolean} boolean indicating whether an input value is a supported legend direction
+*
+* @example
+* var bool = isLegendDirection( 'horizontal' );
+* // returns true
+*
+* bool = isLegendDirection( 'vertical' );
+* // returns true
+*
+* bool = isLegendDirection( 'bar' );
+* // returns false
+*
+* bool = isLegendDirection( 'foo' );
+* // returns false
+*/
+var isLegendDirection = contains( values() );
+
+
+// EXPORTS //
+
+module.exports = isLegendDirection;
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/package.json b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/package.json
new file mode 100644
index 000000000000..e367e5e4f1f4
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/package.json
@@ -0,0 +1,70 @@
+{
+  "name": "@stdlib/plot/vega/base/assert/is-legend-direction",
+  "version": "0.0.0",
+  "description": "Test if an input value is a supported legend direction.",
+  "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",
+    "plot",
+    "base",
+    "vega",
+    "utilities",
+    "utility",
+    "utils",
+    "util",
+    "assert",
+    "test",
+    "check",
+    "is",
+    "valid",
+    "validate",
+    "validation",
+    "isvalid"
+  ],
+  "__stdlib__": {}
+}
diff --git a/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/test/test.js b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/test/test.js
new file mode 100644
index 000000000000..af8ef78042ac
--- /dev/null
+++ b/lib/node_modules/@stdlib/plot/vega/base/assert/is-legend-direction/test/test.js
@@ -0,0 +1,77 @@
+/**
+* @license Apache-2.0
+*
+* Copyright (c) 2026 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 isLegendDirection = require( './../lib' );
+
+
+// TESTS //
+
+tape( 'main export is a function', function test( t ) {
+	t.ok( true, __filename );
+	t.strictEqual( typeof isLegendDirection, 'function', 'main export is a function' );
+	t.end();
+});
+
+tape( 'the function returns `true` if provided a supported legend direction', function test( t ) {
+	var values;
+	var bool;
+	var i;
+
+	values = [
+		'horizontal',
+		'vertical'
+	];
+	for ( i = 0; i < values.length; i++ ) {
+		bool = isLegendDirection( values[ i ] );
+		t.strictEqual( bool, true, 'returns expected value when provided '+values[ i ] );
+	}
+	t.end();
+});
+
+tape( 'the function returns `false` if not provided a supported legend direction', function test( t ) {
+	var values;
+	var bool;
+	var i;
+
+	values = [
+		'',
+		'beep',
+		'boop',
+		'foo',
+		'bar',
+		5,
+		NaN,
+		true,
+		false,
+		null,
+		void 0,
+		[],
+		{},
+		function noop() {}
+	];
+	for ( i = 0; i < values.length; i++ ) {
+		bool = isLegendDirection( values[ i ] );
+		t.strictEqual( bool, false, 'returns expected value when provided '+values[ i ] );
+	}
+	t.end();
+});