Extracting data from plots, images, and maps with WebPlotDigitizer

Screen Shot 2014-06-12 at 1.14.41 PMIt is hard to understand why in today’s all-interactive world, scientific data continues to be represented as still, lifeless images. Sadly, the good old pdf or html versions of research papers do not allow us to extract and reuse the data represented as graphics. While we wait for publishers to finally bring interactive figures to publications, and for data to be more open an easily accessible, a simple and reliable method to extract data from graph would be great. Lucky for us, WebPlotDigitizer does exactly that!

WebPlotDigitizer is a free, online tool, that allows anyone to upload the image of a graph and extract the data. Here are the announced features of the version 3.2 (released in May 2014):

  • Web based. No installation needed.
  • Supports XY charts (even skewed and non-orthogonal), polar plots, ternary diagrams and maps.
  • Automatic curve extraction algorithms aid rapid extraction of a large number of points.
  • Generates data in .CSV format which can be used by any data analysis program like Excel, OpenOffice, Origin etc.
  • A zoomed in view on the side aids accurate selection of data points.
  • Free of charge and distributed under the GNU General Public License Version 3.

This is how it works. First load your the image image of the graph by a simple drag and drop from the webpage or by browsing through your files on your computer. The image can be a screenshot, or even a photograph captured by your webcam since WebPlotDigitizer supports .jpeg, .png, .bmp and .gif. You can then make simple adjustments to the images, flipping or cropping it to your liking. The first step of the analysis consist in defining the type of graph analyzed and calibrating the axis by assigning four points of known values on the axis.

Then comes the extraction of the data points. A manual and an automatic mode are available. In the manual mode, you click directly on the graph to add data points and WebPlotDigitizer calculates the precise coordinates of each point. Simple and reliable but can be time consuming.

The automatic mode uses an extraction algorithm that will automatically identify and extract data points from the image. A few of parameters must be played around with to pinpoint the line or points that you wish to extract. The data can then be exported as a .cvs file or directly plotted using Plot.ly, a web-base graphing tool. The integration of WebPlotDigitizer in Plot.ly really differentiates this tool from the many other solutions, making plotting and sharing the extracted data incredibly easy.

Here are a few useful links to get you started:

And do not hesitate to make a donation to Ankit Rohatgi, creator of this wonderful tool, go to his website and click on donate!

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