For example see examples/3d_surface_plot.rb
Fixed using SPlot with a function wroted by string
forget return io variable in the method store_datasets
Why you've didn't merge its request? BTW using string description of surface function is the great feature of gnuplot. In your current version of ruby_gnuplot one does not work.
I do hope/plan to get to it. I just haven't touched the code for so long I need to run the tests et al again :P
@newmen patches welcome!
sweet demo thanks!