Rendering graphics and plots to a file?

Lua-GD is a binding to the gd library. GD is particularly useful for Web applications, since it creates output in common formats like PNG, JPEG or GIF.

luaplot, mentioned above, can also render directly to graphic file formats.

luagraph is a binding to the Graphviz library, which allows you to visualise visualise complex graphs - that is, in the sense of a set of connected nodes.

This simple interface to gnuplot is useful if you are already familiar with this package and want to integrate it closer with your Lua code.