simple-squiggle/node_modules/mathjs/lib/esm/function/matrix/partitionSelect.js

146 lines
3.9 KiB
JavaScript

import { isMatrix } from '../../utils/is.js';
import { isInteger } from '../../utils/number.js';
import { factory } from '../../utils/factory.js';
var name = 'partitionSelect';
var dependencies = ['typed', 'isNumeric', 'isNaN', 'compare'];
export var createPartitionSelect = /* #__PURE__ */factory(name, dependencies, _ref => {
var {
typed,
isNumeric,
isNaN,
compare
} = _ref;
var asc = compare;
var desc = (a, b) => -compare(a, b);
/**
* Partition-based selection of an array or 1D matrix.
* Will find the kth smallest value, and mutates the input array.
* Uses Quickselect.
*
* Syntax:
*
* math.partitionSelect(x, k)
* math.partitionSelect(x, k, compare)
*
* Examples:
*
* math.partitionSelect([5, 10, 1], 2) // returns 10
* math.partitionSelect(['C', 'B', 'A', 'D'], 1) // returns 'B'
*
* function sortByLength (a, b) {
* return a.length - b.length
* }
* math.partitionSelect(['Langdon', 'Tom', 'Sara'], 2, sortByLength) // returns 'Langdon'
*
* See also:
*
* sort
*
* @param {Matrix | Array} x A one dimensional matrix or array to sort
* @param {Number} k The kth smallest value to be retrieved zero-based index
* @param {Function | 'asc' | 'desc'} [compare='asc']
* An optional comparator function. The function is called as
* `compare(a, b)`, and must return 1 when a > b, -1 when a < b,
* and 0 when a == b.
* @return {*} Returns the kth lowest value.
*/
return typed(name, {
'Array | Matrix, number': function ArrayMatrixNumber(x, k) {
return _partitionSelect(x, k, asc);
},
'Array | Matrix, number, string': function ArrayMatrixNumberString(x, k, compare) {
if (compare === 'asc') {
return _partitionSelect(x, k, asc);
} else if (compare === 'desc') {
return _partitionSelect(x, k, desc);
} else {
throw new Error('Compare string must be "asc" or "desc"');
}
},
'Array | Matrix, number, function': _partitionSelect
});
function _partitionSelect(x, k, compare) {
if (!isInteger(k) || k < 0) {
throw new Error('k must be a non-negative integer');
}
if (isMatrix(x)) {
var size = x.size();
if (size.length > 1) {
throw new Error('Only one dimensional matrices supported');
}
return quickSelect(x.valueOf(), k, compare);
}
if (Array.isArray(x)) {
return quickSelect(x, k, compare);
}
}
/**
* Quickselect algorithm.
* Code adapted from:
* https://blog.teamleadnet.com/2012/07/quick-select-algorithm-find-kth-element.html
*
* @param {Array} arr
* @param {Number} k
* @param {Function} compare
* @private
*/
function quickSelect(arr, k, compare) {
if (k >= arr.length) {
throw new Error('k out of bounds');
} // check for NaN values since these can cause an infinite while loop
for (var i = 0; i < arr.length; i++) {
if (isNumeric(arr[i]) && isNaN(arr[i])) {
return arr[i]; // return NaN
}
}
var from = 0;
var to = arr.length - 1; // if from == to we reached the kth element
while (from < to) {
var r = from;
var w = to;
var pivot = arr[Math.floor(Math.random() * (to - from + 1)) + from]; // stop if the reader and writer meets
while (r < w) {
// arr[r] >= pivot
if (compare(arr[r], pivot) >= 0) {
// put the large values at the end
var tmp = arr[w];
arr[w] = arr[r];
arr[r] = tmp;
--w;
} else {
// the value is smaller than the pivot, skip
++r;
}
} // if we stepped up (r++) we need to step one down (arr[r] > pivot)
if (compare(arr[r], pivot) > 0) {
--r;
} // the r pointer is on the end of the first k elements
if (k <= r) {
to = r;
} else {
from = r + 1;
}
}
return arr[k];
}
});