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Remove dependency of Tree class in IsolationForest #30

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Merged
merged 1 commit into from
Feb 5, 2022
Merged

Remove dependency of Tree class in IsolationForest #30

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29 changes: 11 additions & 18 deletions lib/model/isolation_forest.js
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Original file line number Diff line number Diff line change
@@ -1,5 +1,3 @@
import Tree from '../util/tree.js'

const shuffle = function (arr) {
for (let i = arr.length - 1; i > 0; i--) {
let r = Math.floor(Math.random() * (i + 1))
Expand All @@ -12,7 +10,7 @@ class IsolationTree {
// https://www.slideshare.net/kataware/isolation-forest
// https://cs.nju.edu.cn/zhouzh/zhouzh.files/publication/icdm08b.pdf
constructor() {
this._tree = new Tree({})
this._tree = {}
}

get c() {
Expand Down Expand Up @@ -53,37 +51,32 @@ class IsolationTree {
const nodes = [[this._tree, datas]]
while (nodes.length > 0) {
const [node, data] = nodes.pop()
if (node.isLeaf()) {
const sep = this._separate(data)
if (!sep) {
continue
}
const [f, th] = sep
node.value.feature = f
node.value.threshold = th
node.push({})
node.push({})
const sep = this._separate(data)
if (!sep) {
continue
}
;[node.feature, node.threshold] = sep

const leftData = []
const rightData = []
for (let i = 0; i < data.length; i++) {
if (data[i][node.value.feature] <= node.value.threshold) {
if (data[i][node.feature] <= node.threshold) {
leftData.push(data[i])
} else {
rightData.push(data[i])
}
}
nodes.push([node.at(0), leftData])
nodes.push([node.at(1), rightData])
nodes.push([(node.left = {}), leftData])
nodes.push([(node.right = {}), rightData])
}
}

depth(data) {
return data.map(d => {
let t = this._tree
let depth = 0
while (!t.isLeaf()) {
t = d[t.value.feature] <= t.value.threshold ? t.at(0) : t.at(1)
while (t.left) {
t = d[t.feature] <= t.threshold ? t.left : t.right
depth++
}
return depth
Expand Down