How do I plot lines (not grids) using splot?
If the data in a data file for splot is arranged in such a way that each one has the same number of data points (using blank lines as delimiters, as usual), splot will plot the data with a grid. If you want to plot just lines, use a different number of data entries (you can do this by doubling the last data point, for example). Don’t forget to set parametric mode, of course.