K-Nearest Neighbors Algorithm
To use the K-Nearest Neighbors Algorithm, follow these steps:
- Open the Terminal/SSH and type
node
.
- Classify a data point relative to a labeled data set using the k-nearest neighbors algorithm.
- Map the
data
to objects using Array.prototype.map()
. Each object contains the Euclidean distance of the element from point
, calculated using Math.hypot()
, Object.keys()
, and its label
.
- Use
Array.prototype.sort()
and Array.prototype.slice()
to get the k
nearest neighbors of point
.
- Use
Array.prototype.reduce()
in combination with Object.keys()
and Array.prototype.indexOf()
to find the most frequent label
among them.
Here's an example code that implements the K-Nearest Neighbors Algorithm:
const kNearestNeighbors = (data, labels, point, k = 3) => {
const kNearest = data
.map((el, i) => ({
dist: Math.hypot(...Object.keys(el).map((key) => point[key] - el[key])),
label: labels[i]
}))
.sort((a, b) => a.dist - b.dist)
.slice(0, k);
return kNearest.reduce(
(acc, { label }, i) => {
acc.classCounts[label] =
Object.keys(acc.classCounts).indexOf(label) !== -1
? acc.classCounts[label] + 1
: 1;
if (acc.classCounts[label] > acc.topClassCount) {
acc.topClassCount = acc.classCounts[label];
acc.topClass = label;
}
return acc;
},
{
classCounts: {},
topClass: kNearest[0].label,
topClassCount: 0
}
).topClass;
};
Here's how to use the code:
const data = [
[0, 0],
[0, 1],
[1, 3],
[2, 0]
];
const labels = [0, 1, 1, 0];
kNearestNeighbors(data, labels, [1, 2], 2); // 1
kNearestNeighbors(data, labels, [1, 0], 2); // 0