Pie Chart

fiveworlds · February 16, 2016

My latest way to waste time. Figuring how to make pie charts with javascript and svg. I know google charts gives it to you but they use massive code. Here's my attempt.

<head>
<style>

path{stroke: black; stroke-width: 2;cursor:pointer;stroke-linejoin="round"}
path:hover{stroke: black; stroke-width: 2;opacity:0.5;}
.red{fill: red;}
.green{fill: green;}
.blue{fill: blue;}
.purple{fill: purple;}
.yellow{fill:yellow;}

</style>
  
<script>
function add(a, b) {return a + b;}

var numbers = [30,40,20,50,77];
var colors = ["red","green","blue","purple","yellow"];
var labels = ["red","green","blue","purple","yellow"];
var piechart;
var title = "pie chart";
var total = numbers.reduce(add,0);
var radius = 135;
var startx = 150;
var starty = 240;
var lastx = radius;
var lasty = 0;
var seg = 0;
var rectx = 420;
var recty = 140;
var textx = 470;
var texty = 156;
var collate = "<svg width='800' height='500'>";
var collate1 = "";
var title = "<text x='240' y='50' style='font-size: 36;font-weight: bold;fill: #0099ff;stroke: black;stroke-width: 2'>"+title+"</text></svg>";
  
for (i = 0; i < numbers.length; i++) {

	arc = "0";
	seg = (numbers[i]/total) * 360+seg;		
	if ((numbers[i]/total) > 180){arc = "1";}
	radseg = seg * (Math.PI/180);
	nextx = Math.cos(radseg) * radius;
	nexty = Math.sin(radseg) * radius;
	minuslasty = - lasty;
	nextxminuslasty = - (nextx - lasty);
	nextxminuslastx = nextx - lastx;
	nextyminuslasty = - (nexty - lasty);
	percentage= (numbers[i]/total) * 100;
	collate = collate + "<path class='"+colors[i]+"' d='M " + startx + "," + starty + " l " + lastx + "," + minuslasty + " a" + radius + "," + radius + " 0 " + arc + ",0 " + nextxminuslastx + ","+ nextyminuslasty + " z' />";
	collate1 = collate1 + "<rect x='"+rectx+"' y='"+recty+"' width='30' height='20' class='"+colors[i]+"' /><text x='"+textx+"' y='"+texty+"' >"+labels[i]+" "+percentage+"%</text>";
	lastx=nextx;
	lasty=nexty;
	texty=texty+40;
	recty=recty+40;
}
piechart=collate+" <circle cx='150' cy='240' r='80' stroke='black' stroke-width='3' fill='white' />"+collate1+title;
document.write(piechart);
  </script>
</head>

Edited February 16, 2016 by fiveworlds

Sensei · February 16, 2016

It's working quite well.

You don't have to make add() function at all,

you can inline it,

like it is showed here:

https://developer.mozilla.org/pl/docs/Web/JavaScript/Referencje/Obiekty/Array/Reduce

Edited February 16, 2016 by Sensei

PeterOtt · February 22, 2016

Lol!

But really its worth learning. You can try it with different languages as well.

fiveworlds · February 26, 2016

It's working quite well.

I thought it was too until I tried numbers taking more than 50% of the pie chart.

You don't have to make add() function at all,

Didn't know that learned something new. I fixed the error I had with the pie chart. I also added a random color picker,

var width = 200;
var height = width;
var numbers = [200, 10, 20, 60, 12, 10];
var total = numbers.reduce(function(a, b) {return a + b;});
var piechart = "";
var startx = width / 2;
var starty = startx;
var radius = width / 2 - 10;
var deg = total / 360;
var half = total / 2;
var dx = radius;
var dy = 0;
var lastangle = 0;
var angle = 0;
var radseg = 0;
var arc = 0;
var i = 0;
var ax = 0;
var ay = 0;
var adx = 0;
var ady = 0;
var nextx = 0;
var nexty = 0;
var beginning = "<svg width='" + width + "' height='" + height + "'>";
var end = "</svg>";
var color = "";
for (i = 0; i < numbers.length; i += 1) {
    angle = lastangle + numbers[i] / deg;
    radseg = angle * (Math.PI / 180);
    nextx = Math.cos(radseg) * radius;
    nexty = Math.sin(radseg) * radius;
    color = '#' + (0x1000000 + (Math.random()) * 0xffffff).toString(16).substr(1,6);
    if (numbers[i] > half) {
        arc = 1;
    } else {
        arc = 0;
    }
    ax = startx + nextx;
    ay = starty + nexty;
    adx = startx + dx;
    ady = starty + dy;
    piechart += "\n";
    piechart +=  "<path d=\"M" + startx + "," + starty;
    piechart += " L" + adx + " , " + ady;
    piechart +=  " A" + radius + " , " + radius + " 0 " + arc + " , " + " 1 " + ax + " , " + ay;
    piechart +=  " z\" ";
    piechart +=  " fill=\"" + color + "\" stroke=\"black\" stroke-width=\"2\" ";
    piechart +=  " fill-opacity=\"1\" stroke-linejoin=\"round\" />";
    dx = nextx;
    dy = nexty;
    lastangle = angle;
}
document.write(beginning + piechart + end);

I am going to try for a piechart tag under svg eventually.

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