It’s a common task among scientists to have to extract data from a plot when the raw numbers aren’t available. Today I found a webapp that does this the right way: Web Plot Digitizer, by Ankit Rohatgi.

The complaint I usually have about these digitizer applications is that they’re nonintuitive. Extracting data is fundamentally a simple process: define the coordinate system, then click points and the program tells you their coordinates. And that’s all Web Plot Digitizer does. It even has clearly labeled buttons at each step so that it’s not too hard to figure out what to click when. Most other digitizing programs have a lot of extra buttons which do things that I usually don’t manage to figure out, and they may give them fancy names so that you’re not sure what to click to get to the numbers. But not so with this one. Pretty much all it takes to use the program is shown in this one sequence of screenshots, from the app’s website:

Next time you’re staring at a plot, give this a look!