I'm trying to find the quantity of energy transferred between two systems. I have an absorption curve and a drive curve, but neither of these follow a mathematical expression, they're random squiggely lines. I want to use the absorption curves to find out how much of the drive is being transferred. I know one way to do this would be to integrate the curves, but they can't really be approximated by an expression. How else might I go about it? I have actually thought about drawing them, then doing the old cutting out and measuring the area trick for a rough estimation. Surely there's something easier and more accurate than that though. Maybe scan them and use something on the computer to find the enclosed area? But there's a lot of sharp deviation on the curves, so I'd really need to cut the x-axis up into a lot of sections to get any kind of accuracy whatsoever. Is there any online software that I can draw the curves in (dragging points), or something like that?