logspace.js (2405B)
1 /** 2 * @license Apache-2.0 3 * 4 * Copyright (c) 2018 The Stdlib Authors. 5 * 6 * Licensed under the Apache License, Version 2.0 (the "License"); 7 * you may not use this file except in compliance with the License. 8 * You may obtain a copy of the License at 9 * 10 * http://www.apache.org/licenses/LICENSE-2.0 11 * 12 * Unless required by applicable law or agreed to in writing, software 13 * distributed under the License is distributed on an "AS IS" BASIS, 14 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 15 * See the License for the specific language governing permissions and 16 * limitations under the License. 17 */ 18 19 'use strict'; 20 21 // MODULES // 22 23 var pow = require( '@stdlib/math/base/special/pow' ); 24 var isNumber = require( '@stdlib/assert/is-number' ).isPrimitive; 25 var isNonNegativeInteger = require( '@stdlib/assert/is-nonnegative-integer' ).isPrimitive; 26 var isnan = require( '@stdlib/math/base/assert/is-nan' ); 27 28 29 // MAIN // 30 31 /** 32 * Generates a logarithmically spaced numeric array. 33 * 34 * @param {number} a - exponent of start value 35 * @param {number} b - exponent of end value 36 * @param {NonNegativeInteger} [len=10] - length of output array 37 * @throws {TypeError} first argument must be numeric 38 * @throws {TypeError} second argument must be numeric 39 * @throws {TypeError} third argument must be a nonnegative integer 40 * @returns {Array} logarithmically spaced numeric array 41 * 42 * @example 43 * var arr = logspace( 0, 2, 6 ); 44 * // returns [ 1, ~2.5, ~6.31, ~15.85, ~39.81, 100 ] 45 */ 46 function logspace( a, b, len ) { 47 var arr; 48 var end; 49 var tmp; 50 var d; 51 var i; 52 if ( !isNumber( a ) || isnan( a ) ) { 53 throw new TypeError( 'invalid argument. Exponent of start value must be numeric. Value: `' + a + '`.' ); 54 } 55 if ( !isNumber( b ) || isnan( b ) ) { 56 throw new TypeError( 'invalid argument. Exponent of stop value must be numeric. Value: `' + b + '`.' ); 57 } 58 if ( arguments.length < 3 ) { 59 len = 10; 60 } else { 61 if ( !isNonNegativeInteger( len ) ) { 62 throw new TypeError( 'invalid argument. Length must be a nonnegative integer. Value: `' + len + '`.' ); 63 } 64 if ( len === 0 ) { 65 return []; 66 } 67 } 68 // Calculate the increment: 69 end = len - 1; 70 d = ( b-a ) / end; 71 72 // Build the output array... 73 arr = []; 74 tmp = a; 75 arr.push( pow( 10, tmp ) ); 76 for ( i = 1; i < end; i++ ) { 77 tmp += d; 78 arr.push( pow( 10, tmp ) ); 79 } 80 arr.push( pow( 10, b ) ); 81 return arr; 82 } 83 84 85 // EXPORTS // 86 87 module.exports = logspace;