[$] New features in gnuplot 5.4

Gnuplot 5.4 has been released, three years after the last major release of the free-softwaregraphing program.In this article we will take a look at five major new capabilities in gnuplot.First, we briefly visit voxel plotting, for visualizing 3D data. Since this isa big subject and the most significant addition to the program, we'll save the detailsfor a subsequent article. Next, we learn about plotting polygons in 3D, another completelynew gnuplot feature. After that, we'll get caught up briefly in spider plots, using themto display some recent COVID-19 infection data. Then we'll see an example of how touse pixmaps, a new feature allowing for the embedding of pictures alongside curves orsurfaces. Finally, we'll look at some more COVID-19 data using the new 3D bar chart.