Creates sample data for an SIR model plot

sir-data-generator.js

const fs = require("fs");

const TOTAL_POPULATION = 100000;
const INITIAL_INFECTED_POPULATION = 1;
const ALPHA = 1;
const BETA = 3;
const TIME_TICK = 0.1;
const MAXIMUM_TIME = 20;

if (TIME_TICK <= 0) throw new Error("Time tick must be greater than zero");
if (INITIAL_INFECTED_POPULATION > TOTAL_POPULATION)
  throw new Error(
    "Infected population cannot be larger than the total population"
  );

function writeToFile({ component, content }) {
  try {
    fs.writeFileSync(`sir-data-${component.toLowerCase()}.dat`, content);
    //file written successfully
  } catch (err) {
    console.error(err);
  }
}

function computeAndSaveToFile() {
  const I_ar = [];
  const S_ar = [];
  const R_ar = [];
  const t_ar = [];

  let S = TOTAL_POPULATION;
  let I = INITIAL_INFECTED_POPULATION;
  let R = 0;

  for (let t = 0; t <= MAXIMUM_TIME; t += TIME_TICK) {
    const delS = ((-BETA * S * I) / TOTAL_POPULATION) * TIME_TICK;
    const delI =
      ((BETA * S * I) / TOTAL_POPULATION) * TIME_TICK - ALPHA * I * TIME_TICK;
    const delR = ALPHA * I * TIME_TICK;
    S += delS;
    I += delI;
    R += delR;
    I_ar.push(I);
    S_ar.push(S);
    R_ar.push(R);
    t_ar.push(Number(t.toFixed(2)));
  }

  saveFiles({ t: t_ar, S: S_ar, I: I_ar, R: R_ar });
}

function saveFiles({ t, S, I, R }) {
  let content_S = "x y\n";
  let content_I = "x y\n";
  let content_R = "x y\n";

  for (let i = 0; i < t.length; i++) {
    content_S += `${t[i]} ${S[i]}\n`;
    content_I += `${t[i]} ${I[i]}\n`;
    content_R += `${t[i]} ${R[i]}\n`;
  }

  writeToFile({ component: "s", content: content_S });
  writeToFile({ component: "i", content: content_I });
  writeToFile({ component: "r", content: content_R });
}

computeAndSaveToFile();

Based on this gist.