challenge 165, task 2 in node/typescript

This was hard. I learned a lot about the types. Also had to fix a few
things I did wrong in task 1.

4 files changed, 89 insertions, 10 deletions

diff --git a/challenge-165/julien-fiegehenn/typescript/.nvmrc b/challenge-165/julien-fiegehenn/typescript/.nvmrc
new file mode 100644
index 0000000000..b0c352f157
--- /dev/null
+++ b/challenge-165/julien-fiegehenn/typescript/.nvmrc
@@ -0,0 +1 @@
+v11
\ No newline at end of file
diff --git a/challenge-165/julien-fiegehenn/typescript/ch-1.ts b/challenge-165/julien-fiegehenn/typescript/ch-1.ts
index 32a611a2f9..3df99b09f7 100644
--- a/challenge-165/julien-fiegehenn/typescript/ch-1.ts
+++ b/challenge-165/julien-fiegehenn/typescript/ch-1.ts
@@ -27,11 +27,15 @@
 // Then, generate an SVG file plotting all points, and all lines.
 // If done correctly, you can view the output .svg file in your browser.
 
-import { Plot, PlotData } from "./plot";
+import { Plot, PlotPoint, PlotLine } from "./plot";
 
 const input: string = `53,10
 53,10,23,30
 23,30`;
 
-const plot = new Plot(input.split("\n").map((line) => line.split(",")));
+const plot: Plot = new Plot(
+  input
+    .split("\n")
+    .map((line) => line.split(",").map(parseInt) as PlotPoint | PlotLine)
+);
 plot.toSvg();
diff --git a/challenge-165/julien-fiegehenn/typescript/ch-2.ts b/challenge-165/julien-fiegehenn/typescript/ch-2.ts
new file mode 100644
index 0000000000..6177c7968d
--- /dev/null
+++ b/challenge-165/julien-fiegehenn/typescript/ch-2.ts
@@ -0,0 +1,67 @@
+#!/usr/bin/env node
+
+// Task 2: Line of Best Fit
+// When you have a scatter plot of points, a line of best fit is the line that
+// best describes the relationship between the points, and is very useful in
+// statistics. Otherwise known as linear regression, here is an example of what
+// such a line might look like:
+//
+// The method most often used is known as the least squares method, as it is
+// straightforward and efficient, but you may use any method that generates
+// the correct result.
+//
+// Calculate the line of best fit for the following 48 points
+//
+// 333,129  39,189 140,156 292,134 393,52  160,166 362,122  13,193
+// 341,104 320,113 109,177 203,152 343,100 225,110  23,186 282,102
+// 284,98  205,133 297,114 292,126 339,112 327,79  253,136  61,169
+// 128,176 346,72  316,103 124,162  65,181 159,137 212,116 337,86
+// 215,136 153,137 390,104 100,180  76,188  77,181  69,195  92,186
+// 275,96  250,147  34,174 213,134 186,129 189,154 361,82  363,89
+//
+// Using your rudimentary graphing engine from Task #1, graph all points,
+// as well as the line of best fit.
+
+import { Plot, PlotData, PlotPoint } from "./plot";
+
+const input: string = `333,129  39,189 140,156 292,134 393,52  160,166 362,122  13,193
+341,104 320,113 109,177 203,152 343,100 225,110  23,186 282,102
+284,98  205,133 297,114 292,126 339,112 327,79  253,136  61,169
+128,176 346,72  316,103 124,162  65,181 159,137 212,116 337,86
+215,136 153,137 390,104 100,180  76,188  77,181  69,195  92,186
+275,96  250,147  34,174 213,134 186,129 189,154 361,82  363,89
+`;
+
+// read the input and get all the points
+const points: PlotData = input
+  .split("\n")
+  .flatMap((line: string) => line.split(/\s+/))
+  .filter((e: string) => !!e)
+  .map((point: string) => point.split(",").map(Number) as PlotPoint);
+
+// get all the bits for the calculation
+const xSquared: number[] = [],
+  xY: number[] = [],
+  allX: number[] = [],
+  allY: number[] = [];
+points.forEach((p: PlotPoint) => {
+  xSquared.push(p[0] ** 2);
+  xY.push(p[0] * p[1]);
+  allX.push(p[0]);
+  allY.push(p[1]);
+});
+const numberOfPoints: number = points.length;
+
+// helper function to sum up the arrays
+const sum = (arr: number[]): number =>
+  arr.reduce((partialSum, a) => partialSum + a, 0);
+// m is the Slope of the line
+const m: number =
+  (numberOfPoints * sum(xY) - sum(allX) * sum(allY)) /
+  (numberOfPoints * sum(xSquared) - sum(allX) ** 2);
+
+// b is the Y interept
+const b: number = (sum(allY) - m * sum(allX)) / numberOfPoints;
+
+const plot: Plot = new Plot([...points, [1, m + b, 400, m * 400 + b]]);
+plot.toSvg();
diff --git a/challenge-165/julien-fiegehenn/typescript/plot.ts b/challenge-165/julien-fiegehenn/typescript/plot.ts
index 59fdcee5d2..cad483a752 100644
--- a/challenge-165/julien-fiegehenn/typescript/plot.ts
+++ b/challenge-165/julien-fiegehenn/typescript/plot.ts
@@ -3,30 +3,33 @@ import * as svg from "svg-builder";
 import { SvgBuilder } from "svg-builder";
 import * as fs from "fs";
 
-type PlotPoint = [number, number];
-type PlotLine = [number, number, number, number];
-export type PlotData = [PlotPoint | PlotLine];
+export type PlotPoint = [number, number];
+export type PlotLine = [number, number, number, number];
+// export type PlotPoint = number[];
+// export type PlotLine = number[];
+export type PlotData = Array<PlotPoint | PlotLine>;
 
 export class Plot {
-  svg: SvgBuilder = svg;
+  private svg: SvgBuilder = svg;
+
+  private size: number = 200;
 
   input: PlotData;
-  constructor(input: any) {
+
+  constructor(input: PlotData) {
     this.input = input;
-    console.log(input);
   }
 
   toSvg(): boolean {
     this.input.forEach((record) => {
       if (record.length === 2) {
-        console.log(record);
         this.addPoint(record);
       } else {
         this.addLine(record);
       }
     });
 
-    this.svg = this.svg.width(200).height(200);
+    this.svg = this.svg.width(this.size).height(this.size);
 
     try {
       fs.writeFileSync("output.svg", this.svg.render());
@@ -44,6 +47,8 @@ export class Plot {
       cx: point[0],
       cy: point[1],
     });
+
+    this.size = Math.max(this.size, ...point);
   }
 
   addLine(line: PlotLine): void {
@@ -56,5 +61,7 @@ export class Plot {
       x2: line[2],
       y2: line[3],
     });
+
+    this.size = Math.max(this.size, ...line);
   }
 }