If you have the plot as a PDF or PostScript file you can sometimes write a script to extract the data directly from the coordinates of the plot elements (for PD

If you have the plot as a PDF or PostScript file you can sometimes write a script to extract the data directly from the coordinates of the plot elements (for PDF, uncompress the file with PDFTK, and then the commands are ~readable text). Sometimes the values extracted from plots contain more precision than values reported in tables. It can be quite fiddly, though, so it might not be worth the effort unless you really need it, or you need to do it a lot with many similar figures.