HTML Canvas
HTML Canvas is perfect for Scatter Plots
HTML Canvas is perfect for Line Graphs
HTML Canvas is perfect for combining Scatter and Lines
Scatter Plots
Source Code
const xArray = [50,60,70,80,90,100,110,120,130,140,150];
const yArray = [7,8,8,9,9,9,10,11,14,14,15];
// Plot Scatter
ctx.fillStyle = "red";
for (let i = 0; i < xArray.length-1; i++) {
let x = xArray[i]*400/150;
let y = yArray[i]*400/15;
ctx.beginPath();
ctx.ellipse(x, y, 2, 3, 0, 0, Math.PI * 2);
ctx.fill();
}
Line Graphs
Source Code
const xMax = canvas.height = canvas.width;
const slope = 1.2;
const intercept = 70;
// Plot Line
ctx.beginPath();
ctx.moveTo(0, intercept);
ctx.lineTo(xMax, xMax * slope + intercept);
ctx.stroke();
Combined
Source Code
let xMax = canvas.height;
let yMax = canvas.width;
let slope = 1.2;
let intercept = 70;
const xArray = [50,60,70,80,90,100,110,120,130,140,150];
const yArray = [7,8,8,9,9,9,10,11,14,14,15];
// Plot Scatter
ctx.fillStyle = "red";
for (let i = 0; i < xArray.length-1; i++) {
let x = xArray[i] * xMax/150;
let y = yArray[i] * yMax/15;
ctx.beginPath();
ctx.ellipse(x, y, 2, 3, 0, 0, Math.PI * 2);
ctx.fill();
}
// Plot Line
ctx.beginPath();
ctx.moveTo(0, intercept);
ctx.lineTo(xMax, xMax * slope + intercept);
ctx.stroke();
Having a Plotter Object is nice when studying Artificial Intelligence:
- Makes AI more Fun
- Makes AI more Visual
- Makes AI more Understandable
Create a Plotter Object
Example
function XYPlotter(id) {
this.canvas = document.getElementById(id);
this.ctx = this.canvas.getContext("2d");
this.xMin = 0;
this.yMin = 0;
this.xMax = this.canvas.width;
this.yMax = this.canvas.height;
.
.
Add a Method for Plotting a Line
Example
this.plotLine = function(x0, y0, x, y, color) {
this.ctx.moveTo(x0, y0);
this.ctx.lineTo(x, y);
this.ctx.strokeStyle = color;
this.ctx.stroke();
}
Add a Method for Transforming XY Values
Example
this.transformXY = function() {
this.ctx.transform(1, 0, 0, -1, 0, this.canvas.height)
}
Add a Method for Plotting Points
Example
this.plotPoints = function(n, xArr, yArr, color, radius = 3) {
for (let i = 0; i < n; i++) {
this.ctx.fillStyle = color;
this.ctx.beginPath();
this.ctx.ellipse(xArr[i], yArr[i], radius, radius, 0, 0, Math.PI * 2);
this.ctx.fill();
}
}
Plot Some Random Points
Example
// Create a Plotter
let myPlotter = new XYPlotter("myCanvas");
// Create random XY Points
numPoints = 500;
const xPoints = Array(numPoints).fill(0).map(function(){return Math.random() * myPlotter.xMax});
const yPoints = Array(numPoints).fill(0).map(function(){return Math.random() * myPlotter.yMax});
// Plot the Points
myPlotter.plotPoints(numPoints, xPoints, yPoints, "blue");
Put the Code in a Library
Source Code
function XYPlotter(id) {
this.canvas = document.getElementById(id);
this.ctx = this.canvas.getContext("2d");
this.xMin = 0;
this.yMin = 0;
this.xMax = this.canvas.width;
this.yMax = this.canvas.height;
// Plot Line Function
this.plotLine = function(x0, y0, x, y, color) {
this.ctx.moveTo(x0, y0);
this.ctx.lineTo(x, y);
this.ctx.strokeStyle = color;
this.ctx.stroke();
}
// Transform XY Function
this.transformXY = function() {
this.ctx.transform(1, 0, 0, -1, 0, this.canvas.height)
}
// Pot Points Function
this.plotPoints = function(n, xArr, yArr, color, radius = 3) {
for (let i = 0; i < n; i++) {
this.ctx.fillStyle = color;
this.ctx.beginPath();
this.ctx.ellipse(xArr[i], yArr[i], radius, radius, 0, 0, Math.PI * 2);
this.ctx.fill();
}
}
} // End Plotter Object
Save it in a file (like "myplotlib.js")
Use it in Your HTML Pages
Now you can add your plotter object to your HTML pages:
