RGraph is a JavaScript charts library based on HTML5 SVG and canvas. RGraph is mature (over 15 years old) and has a wealth of features making it an ideal choice to show charts on your website.

More »


Get the latest version of RGraph (version 6.17) from the download page. There's also older versions available, minified files and links to cdnjs.com hosted libraries.

More »


RGraph can be used for free under the GPL or if that doesn't suit your situation there's an inexpensive (£129) commercial license available.

More »

The quadraticCurveTo function

View example on CodePen

The quadraticCurveTo function can be used to add curves to your canvas. It uses the existing pen position as the start point and then the first two coordinates as the mid-point and the last two coordinates that you give it as the endpoint. The curve that is drawn will not necessarily pass through the mid-point.

Arguments to the function

P0 is not specified on the quadraticCurveTo function - this is done by a moveTo call before the quadraticCurveTo call. As shown below.

An example

    window.onload = function ()
        var canvas  = document.getElementById("cvs");
        var context = canvas.getContext('2d');

        // This is where the curve begins (P0)
        context.moveTo(100, 100);
        context.quadraticCurveTo(150, 50, 200, 100);