About
RGraph is a JavaScript charts library based on
HTML5 SVG and canvas. RGraph is mature (over 17 years
old) and has a wealth of features making it an ideal
choice to use for showing charts on your website.
New HTML datagrid
In the April 2025 release a new datagrid object
was added.
This makes it easy to add static or dynamic data
tables to your pages. It can be used whether you use the
canvas or SVG libraries or entirely standalone.
Download
Get the latest version of RGraph (version 6.22, 24th June 2025) from
the download page. You can read the changelog here. There's also older versions available,
minified files and links to cdnjs.com hosted libraries.
License
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.The rotate function
The rotate function rotates the canvas. There are a couple of things you need to keep in mind if you use this function:
- The canvas is always rotated about the [0,0] coordinate so if you want to rotate around another coordinate (the center for example) you need to translate, do the rotate, and then translate back, like the example below. Or in the case of the example below you can translate to the bottom right corner and do the rotate.
- The angle (which is the argument that you give it) is measured in radians - not degrees. 1 radian is equal to (approximately) 57.30 degrees. So 1 degree is equal to Math.PI / 180 radians. Math.PI is a constant that you can use in javascript.
Arguments to the function
- The angle to rotate the canvas (measured in radians - not degrees)
An example
You can use the function like this:
<script> window.onload = function () { var canvas = document.getElementById("cvs"); var context = canvas.getContext('2d'); // First translate the canvas so that the rotation point is at the bottom right of the canvas context.translate(canvas.width, canvas.height) // Pi radians - which is 180 degrees context.rotate(Math.PI); context.beginPath(); context.moveTo(100, 100); context.lineTo(200, 200); context.stroke(); } </script>