daygram.js

var Canvas = require('canvas'),
    fs = require('fs');

var c = new Canvas(1000, 400);
var ctx = c.getContext('2d');

var w = 1000;

ctx.fillStyle = '#fff';
ctx.fillRect(0, 0, 1000, 400);
ctx.fillStyle = '#000';

var f = fs.readFileSync('keystrokes.log', 'utf8');

var lines = f.split('\n').slice(1);

var minutely = {};

for (var i = 0; i < lines.length; i++) {
    var pts = lines[i].split(',');
    var d = new Date(pts[0] * 1000);
    var n = (d.getHours() * 60) + d.getMinutes();
    if (!minutely[n]) minutely[n] = [];
    minutely[n].push(+pts[1]);
}

var minutes = [];
for (var x in minutely) {
    minutes.push([+x, minutely[x]]);
}

minutes = minutes.sort(function(a, b) { return a[0] - b[0] });

for (var i = 0; i < 24; i++) {
    ctx.fillText(i + ':00', 10 + (i / 24) * w, 370);
}

ctx.fillText('keystroke activity over the course of four months', 10, 385);

minutes.map(function(m) {
    m[1].map(function(j) {
        ctx.fillRect(~~((m[0] / 1440) * w), ~~(350 - j / 4), 1, 1);
    });
});

fs.writeFileSync('daygram.png', c.toBuffer());