feat: add plot/vega/scale/discrete

PR-URL: #9538
Co-authored-by: Athan Reines <kgryte@gmail.com>
Reviewed-by: Athan Reines <kgryte@gmail.com>

Author: gururaj1512

lib/node_modules/@stdlib/plot/vega/scale/discrete/examples/index.js

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+/**
+* @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 DiscreteScale = require( './../lib' );
+
+var scale = new DiscreteScale({
+	'name': 'xScale',
+	'type': 'point'
+});
+
+console.log( scale.toJSON() );

lib/node_modules/@stdlib/plot/vega/scale/discrete/lib/change_event.js

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+/**
+* @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';
+
+// MAIN //
+
+/**
+* Returns a new change event object.
+*
+* @private
+* @param {string} property - property name
+* @returns {Object} event object
+*/
+function event( property ) { // eslint-disable-line stdlib/no-redeclare
+	return {
+		'type': 'update',
+		'source': 'scale',
+		'property': property
+	};
+}
+
+
+// EXPORTS //
+
+module.exports = event;

lib/node_modules/@stdlib/plot/vega/scale/discrete/lib/defaults.js

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+/**
+* @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';
+
+// MAIN //
+
+/**
+* Returns defaults.
+*
+* @private
+* @returns {Object} default options
+*
+* @example
+* var o = defaults();
+* // returns {...}
+*/
+function defaults() {
+	return {
+		// Scale type:
+		'type': 'ordinal'
+	};
+}
+
+
+// EXPORTS //
+
+module.exports = defaults;

lib/node_modules/@stdlib/plot/vega/scale/discrete/lib/index.js

@@ -0,0 +1,42 @@
+/**
+* @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';
+
+/**
+* Discrete scale constructor.
+*
+* @module @stdlib/plot/vega/scale/discrete
+*
+* @example
+* var DiscreteScale = require( '@stdlib/plot/vega/scale/discrete' );
+*
+* var scale = new DiscreteScale({
+*     'name': 'xScale'
+* });
+* // returns <DiscreteScale>
+*/
+
+// MODULES //
+
+var main = require( './main.js' );
+
+
+// EXPORTS //
+
+module.exports = main;

lib/node_modules/@stdlib/plot/vega/scale/discrete/lib/main.js

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+/**
+* @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.
+*/
+
+/* eslint-disable no-restricted-syntax, no-invalid-this */
+
+'use strict';
+
+// MODULES //
+
+var logger = require( 'debug' );
+var isObject = require( '@stdlib/assert/is-object' );
+var setReadWriteAccessor = require( '@stdlib/utils/define-read-write-accessor' );
+var setNonEnumerableReadOnly = require( '@stdlib/utils/define-nonenumerable-read-only-property' );
+var setNonEnumerableReadOnlyAccessor = require( '@stdlib/utils/define-nonenumerable-read-only-accessor' ); // eslint-disable-line id-length
+var hasProp = require( '@stdlib/assert/has-property' );
+var inherit = require( '@stdlib/utils/inherit' );
+var objectKeys = require( '@stdlib/utils/keys' );
+var transformErrorMessage = require( '@stdlib/plot/vega/base/transform-validation-message' );
+var instance2json = require( '@stdlib/plot/vega/base/to-json' );
+var Scale = require( '@stdlib/plot/vega/scale/base/ctor' );
+var format = require( '@stdlib/string/format' );
+var properties = require( './properties.json' );
+var defaults = require( './defaults.js' );
+
+// Note: keep the following in alphabetical order according to the `require` path...
+var getProperties = require( './properties/get.js' );
+
+var getType = require( './type/get.js' );
+var setType = require( './type/set.js' );
+
+
+// VARIABLES //
+
+var debug = logger( 'vega:discrete-scale:main' );
+
+
+// MAIN //
+
+/**
+* Discrete scale constructor.
+*
+* @constructor
+* @param {Options} options - constructor options
+* @param {string} options.name - scale name
+* @param {(Collection|Object|Signal)} [options.domain] - domain of associated data values
+* @param {number} [options.domainMax] - maximum value in the scale domain (overrides the `domain` option)
+* @param {number} [options.domainMin] - minimum value in the scale domain (overrides the `domain` option)
+* @param {number} [options.domainMid] - single mid-point value inserted into a two-element domain
+* @param {Collection} [options.domainRaw] - array of raw domain values which overrides the `domain` property
+* @param {(string|Object)} [options.interpolate] - scale range interpolation method
+* @param {(Collection|Object|Signal|string)} [options.range] - scale range
+* @param {boolean} [options.reverse=false] - boolean indicating whether to reverse the order of the scale range
+* @param {boolean} [options.round=false] - boolean indicating whether to round numeric output values to integers
+* @param {string} [options.type='ordinal'] - scale type
+* @throws {TypeError} options argument must be an object
+* @throws {Error} must provide valid options
+* @returns {DiscreteScale} scale instance
+*
+* @example
+* var scale = new DiscreteScale({
+*     'name': 'xScale'
+* });
+* // returns <DiscreteScale>
+*/
+function DiscreteScale( options ) {
+	var opts;
+	var keys;
+	var v;
+	var k;
+	var i;
+	if ( !( this instanceof DiscreteScale ) ) {
+		return new DiscreteScale( options );
+	}
+	if ( !isObject( options ) ) {
+		throw new TypeError( format( 'invalid argument. Options argument must be an object. Value: `%s`.', options ) );
+	}
+	// Check for required properties...
+	if ( !hasProp( options, 'name' ) ) {
+		throw new TypeError( 'invalid argument. Options argument must specify the scale name.' );
+	}
+	Scale.call( this, {
+		'name': options.name
+	});
+
+	// Resolve the default configuration:
+	opts = defaults();
+
+	// Set internal properties according to the default configuration...
+	keys = objectKeys( opts );
+	for ( i = 0; i < keys.length; i++ ) {
+		k = keys[ i ];
+		this[ '_'+k ] = opts[ k ];
+	}
+	// Validate provided options by attempting to assign option values to corresponding fields...
+	for ( i = 0; i < properties.length; i++ ) {
+		k = properties[ i ];
+		if ( !hasProp( options, k ) ) {
+			continue;
+		}
+		v = options[ k ];
+		try {
+			this[ k ] = v;
+		} catch ( err ) {
+			debug( 'Encountered an error. Error: %s', err.message );
+
+			// FIXME: retain thrown error type
+			throw new Error( transformErrorMessage( err.message ) );
+		}
+	}
+	return this;
+}
+
+/*
+* Inherit from a parent prototype.
+*/
+inherit( DiscreteScale, Scale );
+
+/**
+* Constructor name.
+*
+* @private
+* @name name
+* @memberof DiscreteScale
+* @readonly
+* @type {string}
+*/
+setNonEnumerableReadOnly( DiscreteScale, 'name', 'DiscreteScale' );
+
+/**
+* Scale properties.
+*
+* @name properties
+* @memberof DiscreteScale.prototype
+* @type {Array<string>}
+*
+* @example
+* var scale = new DiscreteScale({
+*     'name': 'xScale'
+* });
+*
+* var v = scale.properties;
+* // returns [...]
+*/
+setNonEnumerableReadOnlyAccessor( DiscreteScale.prototype, 'properties', getProperties );
+
+/**
+* Scale type.
+*
+* @name type
+* @memberof DiscreteScale.prototype
+* @type {string}
+* @default 'ordinal'
+*
+* @example
+* var scale = new DiscreteScale({
+*     'name': 'xScale'
+* });
+*
+* var v = scale.type;
+* // returns 'ordinal'
+*/
+setReadWriteAccessor( DiscreteScale.prototype, 'type', getType, setType );
+
+/**
+* Serializes an instance to a JSON object.
+*
+* ## Notes
+*
+* -   This method is implicitly invoked by `JSON.stringify`.
+*
+* @name toJSON
+* @memberof DiscreteScale.prototype
+* @type {Function}
+* @returns {Object} JSON object
+*
+* @example
+* var scale = new DiscreteScale({
+*     'name': 'xScale'
+* });
+*
+* var v = scale.toJSON();
+* // returns {...}
+*/
+setNonEnumerableReadOnly( DiscreteScale.prototype, 'toJSON', function toJSON() {
+	return instance2json( this, properties );
+});
+
+
+// EXPORTS //
+
+module.exports = DiscreteScale;

lib/node_modules/@stdlib/plot/vega/scale/discrete/lib/properties.json

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+[
+  "domain",
+  "domainMax",
+  "domainMin",
+  "domainMid",
+  "domainRaw",
+  "interpolate",
+  "name",
+  "range",
+  "reverse",
+  "round",
+  "type"
+]