add new diagram k-nearest-neighbors.typ and assets

Author: janosh

assets/k-nearest-neighbors/k-nearest-neighbors-hd.png

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+#import "@preview/cetz:0.3.4": canvas, draw
+#import draw: line, content, circle, polygon
+
+#set page(width: auto, height: auto, margin: 8pt)
+#set text(weight: "bold")
+
+
+// Draw a star directly with lines
+#let draw-star(pos, size: 0.3, fill: red) = {
+  let outer-r = size
+  let inner-r = size * 0.4
+
+  let points = ()
+  for idx in range(10) {
+    let angle = idx * 36deg
+    let radius = if calc.rem(idx, 2) == 0 { outer-r } else { inner-r }
+    points.push((
+      pos.at(0) + radius * calc.cos(angle),
+      pos.at(1) + radius * calc.sin(angle),
+    ))
+  }
+
+  // Draw connected lines to form a star
+  for idx in range(10) {
+    let next = if idx == 9 { 0 } else { idx + 1 }
+    line(
+      points.at(idx),
+      points.at(next),
+      stroke: 1.5pt,
+      fill: fill,
+    )
+  }
+
+  if fill != none {
+    line(..points, close: true, stroke: none, fill: fill)
+  }
+}
+
+// Draw a triangle using polygon function
+#let draw-triangle(pos, size: 0.275, fill: green) = {
+  polygon(
+    pos,
+    3,
+    radius: size,
+    angle: 90deg, // Point up
+    fill: fill,
+    stroke: .5pt,
+  )
+}
+
+#canvas({
+  // Set up coordinate system
+  let arrow-style = (mark: (end: "stealth", fill: black, scale: 0.7))
+  let axis-length = 6
+
+  // Draw axes
+  line(
+    (0, 0),
+    (axis-length, 0),
+    ..arrow-style,
+    name: "x-axis",
+  )
+  content((rel: (-0.1, 0.2), to: "x-axis.end"), [$x$ axis], anchor: "south-east")
+
+  line((0, 0), (0, axis-length), ..arrow-style, name: "y-axis")
+  content((rel: (0.2, -0.1), to: "y-axis.end"), [$y$ axis], anchor: "north-west")
+
+  // Draw Class A (red stars)
+  draw-star((1.6, 4.0))
+  draw-star((1.3, 3.5))
+  draw-star((2.3, 3.8))
+  draw-star((1.8, 3.0))
+  draw-star((1.6, 2.7))
+  draw-star((2.5, 2.5))
+  draw-star((2, 2.2))
+
+  // Draw Class B (green triangles)
+  draw-triangle((4.2, 3.5))
+  draw-triangle((3.6, 2.8))
+  draw-triangle((3.4, 2.2))
+  draw-triangle((4.0, 2.2))
+  draw-triangle((5.2, 2.5))
+  draw-triangle((4.7, 3.5))
+  draw-triangle((4, 1.5))
+  draw-triangle((4.7, 1.8))
+
+  // Draw the new example to classify (yellow square with question mark)
+  content(
+    (3, 2.5),
+    (rel: (0.4, 0.4)),
+    align(center, text(baseline: 1.5pt)[?]),
+    anchor: "center",
+    frame: "rect",
+    fill: yellow,
+    padding: 1pt,
+    name: "new-example",
+  )
+
+  // Draw the k=3 and k=7 circles centered at the new example
+  circle(
+    "new-example.center",
+    radius: 0.8,
+    stroke: (dash: "dashed"),
+    name: "k3-circle",
+  )
+  content((rel: (0, -0.3), to: "k3-circle.south"), $k = 3$, anchor: "north")
+
+  circle(
+    "new-example.center",
+    radius: 2.0,
+    stroke: (dash: "dashed"),
+    name: "k7-circle",
+  )
+  content((rel: (0, -0.3), to: "k7-circle.south"), $k = 7$, anchor: "north")
+
+  // Add class labels in the upper right corner
+  content((5.4, 4.8), text(fill: red, size: 12pt)[Class A])
+  content((5.4, 4.3), text(fill: green, size: 12pt)[Class B])
+
+  // Add arrow pointing to the new example
+  content((4, 5.5), [New example\ to classify], name: "new-example-label")
+  line(
+    "new-example-label",
+    "new-example.north",
+    stroke: 0.6pt,
+    mark: (end: "stealth", fill: black, offset: 0.05),
+  )
+})

assets/k-nearest-neighbors/k-nearest-neighbors.pdf

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+title: k-Nearest Neighbors
+tags:
+  - machine learning
+  - classification
+  - data science
+  - algorithms
+  - KNN
+description: This image illustrates the K-Nearest Neighbors classification algorithm, showing how different values of $k$ affect classification results. Red stars represent Class A data points, green triangles represent Class B data points, and the yellow square with a question mark is a new instance to be classified. The dashed circles show the $k=3$ and $k=7$ neighborhoods around the instance.
+source: https://kdnuggets.com/2020/11/most-popular-distance-metrics-knn.html