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 datagrid in v6.21
In version 6.21 a new datagrid object has been 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 6.21, 10th April 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 scale function
The scale function increases or decreases the size of the pixels
on the canvas - scaling them up or scaling them down. If you
use negative values the drawings you make may be off-canvas. So scaling the horizontal
direction by 2 increases the x-axis pixel size making
everything bigger, by 1 and it remains the same, by 0.5 makes things smaller
and negative values cause the x-axis pixel system to
begin being reversed - so they're actually off to the left of the canvas
(which you can't then see).
Arguments to the function
- The
x-axisscale factor that should be applied - The
y-axisscale factor that should be applied
An example
You can use the function like this:
<script>
window.onload = function ()
{
var canvas = document.getElementById("cvs");
var context = canvas.getContext('2d');
// This doubles the size of the canvas in both the X and Y directions
context.scale(2, 2);
context.beginPath();
context.moveTo(0, 0);
context.lineTo(200, 200);
context.stroke();
}
</script>