  It is common for authors to communicate their results in graphical figures,
but those data are frequently unavailable for reanalysis. Reconstructing data
points from a figure manually requires the author to measure the coordinates
either on printed pages using a ruler, or from the display screen using a
cursor. This is time-consuming (often hours) and error-prone, and limited by
the precision of the display or ruler. What is often not realised is that the
data themselves are held in the PDF document to much higher precision (usually
0.0-0.01 pixels), if the figure is stored in vector format. We developed alpha
software to automatically reconstruct data from vector figures and tested it on
funnel plots in the meta-analysis literature. Our results indicate that
reconstructing data from vector based figures is promising, where we correctly
extracted data for 12 out of 24 funnel plots with extracted data (50%).
However, we observed that vector based figures are relatively sparse (15 out of
136 papers with funnel plots) and strongly insist publishers to provide more
vector based data figures in the near future for the benefit of the scholarly
community.
