[Gretl-devel] plotting points

This is a consolidated response to some points made lately by Sven about various aspects of graphing/plotting in gretl. 1) There's now a "bars" mode for the --band-style option to "gnuplot' and "plot": when this is given the "band" is plotted using the gnuplot errorbars style. This does not look good if you have a high density of points (ugly "millipede" effect) but it's arguably preferable in the low-density case, since the other styles (lines, dash, fill) may give a spurious impression of continuity of the band. 2) Up till now, the GUI "savename" apparatus for graphs, as in graph1 <- gnuplot ... has masked the gnuplot/plot option --output=display: you got the plot saved as an icon under the specified name, but no window showing the plot (until you double-click on the icon). That's now fixed: you can both save the plot as a named icon and display it in a window without delay. 3) This is a bit more technical. In http://lists.wfu.edu/pipermail/gretl-devel/2016-October/006960.html Sven suggests that we move to require gnuplot 5 for gretl (our current minimum supported gnuplot version is 4.6.0). His reasoning is, "I would like to see gretl handing the data over to gnuplot in the 'multiple-columns-side-by-side' format that gnuplot 5 apparently adopted following Allin's suggestion. It would then be much easier to tweak the appearance of plots beyond the subset functionality that is directly supported by gretl." There are various good reasons for requiring gnuplot 5 but I'm not sure this is one of them. As Sven notes, the new mode of inlining data was something I requested of the gnuplot developers. It has the advantage of compactness: you can inline all the required data in a single block, whereas with the old inlining method (still supported in gnuplot 5) you need a separate data block for each y-axis variable, and the x-axis data have to be repeated in each of these blocks. However, there's something I hadn't thought of when I made that suggestion. Under the old mode, the inlined data follow all the gnuplot commands (typically a bunch of "set" statements followed by a "plot" statement which may have multiple clauses). So all the lines you might wish to tweak are up-front in the gnuplot source file. Under the new mode the single data block is defined as an array variable, which is then referenced by "plot". This means the data block must precede "plot". No big deal, I suppose, if the data are few, but with a dense plot you might have to scroll down through hundreds of lines of data to get to the "plot" clauses (e.g. when editing the plot commands in a gretl window). It seems to me this would be more awkward. Allin