88 lines
2.3 KiB
JavaScript
88 lines
2.3 KiB
JavaScript
/**
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* @license Apache-2.0
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*
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* Copyright (c) 2018 The Stdlib Authors.
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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'use strict';
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// MODULES //
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var pow = require( '@stdlib/math/base/special/pow' );
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var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive;
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var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive;
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var isnan = require( '@stdlib/math/base/assert/is-nan' );
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// MAIN //
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/**
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* Generates a logarithmically spaced numeric array.
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*
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* @param {number} a - exponent of start value
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* @param {number} b - exponent of end value
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* @param {NonNegativeInteger} [len=10] - length of output array
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* @throws {TypeError} first argument must be numeric
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* @throws {TypeError} second argument must be numeric
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* @throws {TypeError} third argument must be a nonnegative integer
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* @returns {Array} logarithmically spaced numeric array
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*
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* @example
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* var arr = logspace( 0, 2, 6 );
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* // returns [ 1, ~2.5, ~6.31, ~15.85, ~39.81, 100 ]
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*/
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function logspace( a, b, len ) {
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var arr;
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var end;
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var tmp;
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var d;
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var i;
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if ( !isNumber( a ) || isnan( a ) ) {
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throw new TypeError( 'invalid argument. Exponent of start value must be numeric. Value: `' + a + '`.' );
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}
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if ( !isNumber( b ) || isnan( b ) ) {
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throw new TypeError( 'invalid argument. Exponent of stop value must be numeric. Value: `' + b + '`.' );
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}
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if ( arguments.length < 3 ) {
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len = 10;
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} else {
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if ( !isNonNegativeInteger( len ) ) {
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throw new TypeError( 'invalid argument. Length must be a nonnegative integer. Value: `' + len + '`.' );
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}
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if ( len === 0 ) {
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return [];
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}
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}
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// Calculate the increment:
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end = len - 1;
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d = ( b-a ) / end;
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// Build the output array...
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arr = [];
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tmp = a;
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arr.push( pow( 10, tmp ) );
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for ( i = 1; i < end; i++ ) {
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tmp += d;
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arr.push( pow( 10, tmp ) );
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}
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arr.push( pow( 10, b ) );
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return arr;
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}
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// EXPORTS //
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module.exports = logspace;
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