Saturday, February 23, 2008


Sometimes I want to "un-plot" data. I find myself in the situation where I have a plot of the data, but not the actual coordinates of the data itself. So, today I wrote this little tool for turning a bitmap image into the x and y coordinates of the curve. (Some Photoshop work may be necessary for cleaning out other lines in the image). It simply takes the image, starts at the top, and scans downwards until it hits the curve, and then works from left to right. The data can be saved as CSV, to be easily loaded into Excel or Matlab.

I've tested this on figures from research papers, and it works. This will be useful for recovering data from a figure when the original data has been lost. Also, I can use it to get audio data from Audacity.

Watch this screencast of it in action. This will show how to use it.

And here is the program (897K). Currently Windows only, but I can port it to Linux if there is interest.


erik_kennedy said...

That's pretty sick! I'm gonna go FFT the stock market or something!

Also, for Audacity, try selecting some data, then Analyze->Plot Spectrum. Useful? Maybe. But thought you might be interested.

Mel said...


Although I suppose the ultimate in cross-platform portability would be to throw this up as a webapp with a rudimentary API (insert url to image here, grab output from this other one).

Ashay said...

This was a really useful application for me.
Thanks for making it.